Every BIOS is different but it will usually be on the summary page or something like that. What you're looking for is if the BIOS reports that the drive is about 137GB (which is a limitation of some BIOSes). If it is, then most likely your /boot partition is past that on your disk so you could either try and resize the partitions or try the Boot-Repair option from Ubuntu.
I think this may be your best option.
Boot with your Ubuntu LiveCD and follow the instructions here
for using the Boot-Repair program.
Make sure you note the URL that it gives that way I can try and help more if it doesn't work.
1. launch Boot-Repair from either :
1. the Dash (the Ubuntu logo at the top-left of the screen)
2. or System->Administration->Boot-Repair menu (Ubuntu 10.04 only)
3. or by typing 'boot-repair' in a terminal
2. Then click the "Recommended repair" button. When repair is finished, note the URL (paste.ubuntu.com/XXXXX) that appeared on a paper, then reboot and check if you recovered access to your OSs.
3. If the repair did not succeed, indicate the URL to people who help you by email or forum.