Oleview has been hanging and taking up all the CPU when I tried to open a typelib on a Vista machine. I saw http://support.microsoft.com/kb/176938 and tried to follow the recommended solution (regsvr32 iviewers.dll), but that did not fix it either. It turns out the solution is to run oleview from a non-elevated cmd prompt. For example, you can just run it from the Run dialog box. I was always running it from an elevated cmd prompt since that's what I am have open for during development.

You wouldn't think that something that works in non-elevated mode would break in elevated mode, but apparantly it happens because of some registry shimming...