This sounds like you have a corrupted dll file somewhere i had a simular problem with missing tools bars and nothing would fix it. trying to find the corupted file is a nightmare i wouldnt recommend to any one.
Did you per chance install a run time version or install a service pack recently ?
there is one drastic suggestion that worked for me which is to uninstall the whole of ms office (if you use outlook back up your PST file first). you then have to reboot the PC and run a utility tool from microsoft called eraser (there are different versions for different Operating systems so be sure you get the correct one)
this removes all the rubbish the the office uninstaller left behind (which is important as the corrupted file will be in this stuff)
then reinstall your ms office and it should (with luck) have solved the problem
for more info read this
hope it helps