So, ... what happend to me is very strange ...

I installed Mandriva 2006.0 a few days ago. I'm not new in Linux, I use it since 5-6 years, so, I know what am I doing, at least I thought so...
Today I needed to write a DVD, first time since install. Till today I not even put a CD in my drive(s). From the moment I started K3B it crashed at "Detecting devices...", OK, I killed the process, I tried "X CD Roast" ... the same thing ... it says "Starting detecting devices..." then its window frezes. I restarted my PC several times, I loged in as root ... same problem. Finaly I put in a CD in my CDDrive and I tried to mount it ... the shell got freezed -> no error message, no mounted device. Then I tried my DVD Drive, same problem ... whit a "ps aux" there are the "mount" processes and I can not kill them, even with "kill -9 ..." they remain there.
The most strange thing is that since this problem appeared "Mandriva Linux Control Center" fails to start. Splash screen appears and then ... nothing, I let it on the screen for 10 minutes ...
I tried the "hdc=scsi-ide" switch in lilo, it detected the device, my mount point in /etc/fstab was automaticaly changed to the new scasi device, but still can't mount any disk nor write any.
What else should I say? I have a "Compaq" cdrom on hdd and an LG DVD+-RW on hdc.
If you have any ideeas please help ... and sorry for my bad english.

OK, somehow, now I can get errors ...

/var/log/messeges:

Mar 13 01:01:11 localhost kernel: hdd: DMA interrupt recovery
Mar 13 01:01:11 localhost kernel: hdd: lost interrupt
Mar 13 01:01:17 localhost kernel: hdd: status timeout: status=0xd0 { Busy }
Mar 13 01:01:17 localhost kernel: ide: failed opcode was: unknown
Mar 13 01:01:17 localhost kernel: hdd: drive not ready for command
Mar 13 01:01:17 localhost kernel: SCSI error : <2 0 0 0> return code = 0x6000000
Mar 13 01:01:17 localhost kernel: end_request: I/O error, dev sr1, sector 0
Mar 13 01:01:17 localhost kernel: Buffer I/O error on device sr1, logical block 0
Mar 13 01:01:47 localhost kernel: hdd: DMA interrupt recovery
Mar 13 01:01:47 localhost kernel: hdd: lost interrupt
Mar 13 01:01:52 localhost kernel: hdd: status timeout: status=0xd0 { Busy }
Mar 13 01:01:52 localhost kernel: ide: failed opcode was: unknown
Mar 13 01:01:52 localhost kernel: hdd: drive not ready for command
Mar 13 01:02:22 localhost kernel: hdd: DMA interrupt recovery
Mar 13 01:02:22 localhost kernel: hdd: lost interrupt
Mar 13 01:02:27 localhost kernel: hdd: status timeout: status=0xd0 { Busy }
Mar 13 01:02:27 localhost kernel: ide: failed opcode was: unknown
Mar 13 01:02:27 localhost kernel: hdd: drive not ready for command
Mar 13 01:02:58 localhost kernel: hdd: DMA interrupt recovery
Mar 13 01:02:58 localhost kernel: hdd: lost interrupt
Mar 13 01:03:03 localhost kernel: hdd: status timeout: status=0xd0 { Busy }
Mar 13 01:03:03 localhost kernel: ide: failed opcode was: unknown
Mar 13 01:03:03 localhost kernel: hdd: drive not ready for command
Mar 13 01:03:03 localhost kernel: SCSI error : <2 0 0 0> return code = 0x6000000
Mar 13 01:03:03 localhost kernel: end_request: I/O error, dev sr1, sector 0
Mar 13 01:03:03 localhost kernel: FAT: unable to read boot sector
Mar 13 01:04:43 localhost kernel: FAT: bogus number of reserved sectors
Mar 13 01:04:43 localhost kernel: VFS: Can't find a valid FAT filesystem on dev sr0.
Mar 13 01:05:00 localhost CROND[4785]: (mail) CMD (/usr/bin/python -S /usr/lib/mailman/cron/gate_news)
Mar 13 01:05:13 localhost kernel: attempt to access beyond end of device
Mar 13 01:05:13 localhost kernel: sr0: rw=0, want=68, limit=4
Mar 13 01:05:13 localhost kernel: isofs_fill_super: bread failed, dev=sr0, iso_blknum=16, block=16

/etc/lilo.conf:

...
image=/boot/vmlinuz
label="Linux_Mandriva_2006"
root=/dev/hda3
initrd=/boot/initrd.img
append="acpi=ht resume=/dev/hda5 splash=silent hdc=ide-scsi hdd=ide-scs"
vga=788
...

/etc/fstab:

/dev/hda3 / ext3 noatime 1 1
/dev/sr0 /mnt/cdrom2 auto umask=0,user,iocharset=iso8859-1,sync,codepage=850,noauto,ro,exec,users 0 0
/dev/sr1 /mnt/cdrom3 auto umask=0,user,iocharset=iso8859-1,sync,codepage=850,noauto,ro,exec,users 0 0
none /mnt/floppy supermount dev=/dev/fd0,fs=ext2:vfat,--,umask=0,iocharset=iso8859-1,sync,codepage=850 0 0
/dev/hda1 /mnt/win_c ntfs umask=0,nls=iso8859-1,rw 0 0
/dev/hda6 /mnt/win_d ntfs umask=0,nls=iso8859-1,rw 0 0
/dev/hda7 /mnt/win_e ntfs umask=0,nls=iso8859-1,rw 0 0
none /proc proc defaults 0 0
/dev/hda5 swap swap defaults 0 0

Any attempt to mount manualy a device in the sr0 (DVDRW) results in: "mount: you must specify the filesystem type" same for CD's and DVD's - I tryed iso9660 and autofs ... no luck.
In the CDROM drive sr1, if I put a CD, mount tryes to do its job, but finaly after about 5-10 minutes of trying and rolling my disk it gives me the same error. Of course mount remains unsuccesfull.

I don't know what is the problem with with K3b or X-CD-Roast, but anyway, you must not use 'ide_scsi' - for 2.6+ kernels, scsi commands for the ATAPI writer are sent through the regular 'ide_cd' driver, and 'ide_scsi' conflicts. Check if 'ide_cd' is loaded and 'ide_scsi' is not.