Are you on a PowerPC or Intel machine, and which version of the OS do you have installed?
We have a known bug in the database where keyboard shortcuts involving the control key don't work on PPC machines that are running 10.5. Only that hardware/software combo appears to be affected - shortcuts that worked fine on 10.4 don't work on the same machine when upgraded to 10.5, and Intel machines on either OS work just fine.
In any case, if that description matches your configuration, I'd ask you to copy and paste your report into an email (use the Send Feedback item under the help menu) so the ninjas can attach your info to that bug in our database.
If you're on a different combination of hardware and OS, there's likely something else going on. If you contact the ninjas, we'll work with you to figure out what it is.