Helper application for MS Word

[deipnosophista]

I was trying to do too much at once with Word a while back, and it froze on me. I think a file must have become corrupted, since, since then, I have found that when I try to use the OpenFile command I get the message “helper application not present”. That’s not completely disabling, since I can still open files using the OpenRecent command and also from Finder – but a real problem is that I can’t open Word files from websites. I replaced my Office suite with a newer version (2008), but that hasn’t solved the problem (so presumably the issue is not with Word itself), and a couple of casual enquiries of high street consultants were met with bafflement. I've since bought a new iMac and the problem still persists. Anyone know what I can do?