I am running -current, and I recently had to reboot. Subsequently I have had trouble installing the nvidia drivers and getting X to start. When my machine boots up, I get a great number of warnings and errors about i2c related symbols and parameters. Here is a dump of `dmesg | grep i2c_`:

i2c_core: Unknown parameter `i2c_debug'
i2c_viapro: Unknown symbol i2c_del_adapter
i2c_viapro: Unknown symbol i2c_add_adapter
i2c_core: Unknown parameter `i2c_debug'
i2c_core: Unknown parameter `i2c_debug'
tveeprom: Unknown symbol i2c_probe
tveeprom: Unknown symbol i2c_master_recv
tveeprom: Unknown symbol i2c_register_driver
tveeprom: Unknown symbol i2c_del_driver
tveeprom: Unknown symbol i2c_detach_client
tveeprom: Unknown symbol i2c_attach_client
tveeprom: Unknown symbol i2c_master_send
tveeprom: Unknown symbol i2c_probe
tveeprom: Unknown symbol i2c_master_recv
tveeprom: Unknown symbol i2c_register_driver
tveeprom: Unknown symbol i2c_del_driver
tveeprom: Unknown symbol i2c_detach_client
tveeprom: Unknown symbol i2c_attach_client
tveeprom: Unknown symbol i2c_master_send
i2c_algo_bit: Unknown symbol i2c_del_adapter
i2c_algo_bit: Unknown symbol i2c_add_adapter
i2c_algo_bit: Unknown symbol i2c_del_adapter
i2c_algo_bit: Unknown symbol i2c_add_adapter
bttv: Unknown symbol i2c_bit_add_bus
bttv: Unknown symbol i2c_master_recv
bttv: Unknown symbol i2c_del_adapter
bttv: Unknown symbol i2c_bit_del_bus
bttv: Unknown symbol i2c_clients_command
bttv: Unknown symbol i2c_add_adapter
bttv: Unknown symbol i2c_master_send
bttv: Unknown symbol i2c_bit_add_bus
bttv: Unknown symbol i2c_master_recv
bttv: Unknown symbol i2c_del_adapter
bttv: Unknown symbol i2c_bit_del_bus
bttv: Unknown symbol i2c_clients_command
bttv: Unknown symbol i2c_add_adapter
bttv: Unknown symbol i2c_master_send
i2c_core: Unknown parameter `i2c_debug'
tveeprom: Unknown symbol i2c_probe
tveeprom: Unknown symbol i2c_master_recv
tveeprom: Unknown symbol i2c_register_driver
tveeprom: Unknown symbol i2c_del_driver
tveeprom: Unknown symbol i2c_detach_client
tveeprom: Unknown symbol i2c_attach_client
tveeprom: Unknown symbol i2c_master_send
i2c_algo_bit: Unknown symbol i2c_del_adapter
i2c_algo_bit: Unknown symbol i2c_add_adapter
bttv: Unknown symbol i2c_bit_add_bus
bttv: Unknown symbol i2c_master_recv
bttv: Unknown symbol i2c_del_adapter
bttv: Unknown symbol i2c_bit_del_bus
bttv: Unknown symbol i2c_clients_command
bttv: Unknown symbol i2c_add_adapter
bttv: Unknown symbol i2c_master_send
i2c_core: Unknown parameter `i2c_debug'
tveeprom: Unknown symbol i2c_probe
tveeprom: Unknown symbol i2c_master_recv
tveeprom: Unknown symbol i2c_register_driver
tveeprom: Unknown symbol i2c_del_driver
tveeprom: Unknown symbol i2c_detach_client
tveeprom: Unknown symbol i2c_attach_client
tveeprom: Unknown symbol i2c_master_send
i2c_algo_bit: Unknown symbol i2c_del_adapter
i2c_algo_bit: Unknown symbol i2c_add_adapter
bttv: Unknown symbol i2c_bit_add_bus
bttv: Unknown symbol i2c_master_recv
bttv: Unknown symbol i2c_del_adapter
bttv: Unknown symbol i2c_bit_del_bus
bttv: Unknown symbol i2c_clients_command
bttv: Unknown symbol i2c_add_adapter
bttv: Unknown symbol i2c_master_send
i2c_core: Unknown parameter `i2c_debug'
i2c_viapro: Unknown symbol i2c_del_adapter
i2c_viapro: Unknown symbol i2c_add_adapter
i2c_core: Unknown parameter `i2c_debug'
i2c_viapro: Unknown symbol i2c_del_adapter
i2c_viapro: Unknown symbol i2c_add_adapter
i2c_core: Unknown parameter `i2c_debug'
i2c_isa: Unknown symbol i2c_adapter_dev_release
i2c_isa: Unknown symbol i2c_adapter_driver
i2c_isa: Unknown symbol i2c_bus_type
i2c_isa: Unknown symbol i2c_adapter_class
i2c_core: Unknown parameter `i2c_debug'
eeprom: Unknown symbol i2c_probe
eeprom: Unknown symbol i2c_register_driver
eeprom: Unknown symbol i2c_smbus_write_byte
eeprom: Unknown symbol i2c_smbus_read_byte
eeprom: Unknown symbol i2c_smbus_read_i2c_block_data
eeprom: Unknown symbol i2c_del_driver
eeprom: Unknown symbol i2c_detach_client
eeprom: Unknown symbol i2c_smbus_read_byte_data
eeprom: Unknown symbol i2c_attach_client
i2c_core: Unknown parameter `i2c_debug'
i2c_isa: Unknown symbol i2c_adapter_dev_release
i2c_isa: Unknown symbol i2c_adapter_driver
i2c_isa: Unknown symbol i2c_bus_type
i2c_isa: Unknown symbol i2c_adapter_class
w83627hf: Unknown symbol i2c_isa_add_driver
w83627hf: Unknown symbol i2c_isa_del_driver
w83627hf: Unknown symbol i2c_detach_client
w83627hf: Unknown symbol i2c_attach_client

Can anyone give me some idea what may be causing this? I2c is compiled as a module, and debugging is enabled. I get these error messages when booting into 2.6.18 and 2.6.16.14.

[Note: subject edited for clarity]

I am getting these messages too:

WARNING: Error inserting i2c_core (/lib/modules/2.6.18/kernel/drivers/i2c/i2c-core.ko): Unknown symbol in module, or unknown parameter (see dmesg)
FATAL: Error inserting i2c_viapro (/lib/modules/2.6.18/kernel/drivers/i2c/busses/i2c-viapro.ko): Unknown symbol in module, or unknown parameter (see dmesg)
WARNING: Error inserting i2c_core (/lib/modules/2.6.18/kernel/drivers/i2c/i2c-core.ko): Unknown symbol in module, or unknown parameter (see dmesg)
FATAL: Error inserting i2c_isa (/lib/modules/2.6.18/kernel/drivers/i2c/busses/i2c-isa.ko): Unknown symbol in module, or unknown
parameter (see dmesg)
WARNING: Error inserting i2c_core (/lib/modules/2.6.18/kernel/drivers/i2c/i2c-core.ko): Unknown symbol in module, or unknown parameter (see dmesg)
FATAL: Error inserting eeprom (/lib/modules/2.6.18/kernel/drivers/i2c/chips/eeprom.ko): Unknown symbol in module, or unknown parameter (see dmesg)
WARNING: Error inserting i2c_core (/lib/modules/2.6.18/kernel/drivers/i2c/i2c-core.ko): Unknown symbol in module, or unknown parameter (see dmesg)
WARNING: Error inserting i2c_isa (/lib/modules/2.6.18/kernel/drivers/i2c/busses/i2c-isa.ko): Unknown symbol in module, or unknown parameter (see dmesg)
FATAL: Error inserting w83627hf (/lib/modules/2.6.18/kernel/drivers/hwmon/w83627hf.ko): Unknown symbol in module, or unknown parameter (see dmesg)

I had the same problem ... in my case the first line gives the clue I searched in /etc/modprobe.d if this option has been set ( ls | xargs grep i2c_debug). In my case it was set in bttv, so I commented it out and rebooted my PC.

When consulting dmesg again all my i2c_core errors were gone

Hope this helps.