i just reinstalled PS myself after breaking my drive doing stuff and haveing to reformat...anyways. mine was getting a runtime error as soon as the GUI was loaded, i went into setup flicked load all maps back off and ran the client, logged in, was ok, logged out, flcik load all maps back on, and it worked.
it's probably not the same problem as yours, but is a possible scenario,
anyways, can you state your comp specs?
run>dxdiag will help if you need to find them out