I in fact had this issue and reinstalled comodo 5 times. I tried a new account etc...nothing. Then I realized, Comodo install file MUST be on C: so if you have another partition and put it on D: per se, or have changed the drive letter , something on that order, it is likely that. After putting the install file back on C:, it worked great, simple but almost got me, lol.
If not,
Do a sys restore to known good working order , if not run Ccleaner, if that fails, go to START \RUN \ type in CMD\ in the box type sfc /scannow (exactly as I put and notice the space between sfc and /) and you may likely need the xp disk. This has a good chance to restore your needed files as somethng has gotten deleted or corrupt. I do suggest uninstalling Comodo first, run ccleaner, and even a simple diskclean utility before sfc. Make sure you are virus and spyware free, very important.
Please think what you may have changed with partitions, setup file moved etc...as mentioned first.
Hope this helps,
Paul