There is a rather long list of “know issues” – potential problems when running Autodesk Inventor 2008 in Windows Vista. See the technical document TS1070153.
Most of these issues are obvious (like no support for OpenGL in Vista, nobody needs it for Inventor with Direct3D), some are too rare to find in a production environment (like limited support for some video codecs for animation), some are more important (like some limitations with the UAC function enabled).
In any case, upgrade to Inventor 2009 and Vista 64 – there are much less Vista-induced limitations (if any) and first of all, the native 64-bit version (with enough RAM) is much faster. Be aware that not all addon applications you might curently use are supported in the 64-bit version of Inventor/Vista.