Unable to do system restore

Not sure if this is an XP or Office issue. Trying to install software
(Delphi 2009) it failed with an unknown error and I had to reboot. All my
office programs now failed to work with different error messages (not enough
memory, can't find fpsrvvtl.dll, can't initialise shared utilities, straight
to the error reporting window and others). All other software seems to work
fine.

Tried Office diagnostics - no problems found.

Tried switching users and everything worked for the other user on the
system.

Tried a system restore to yesterday which appeared to work until the
computer rebooted and I go the error unable to restore to 12 March.

Any ideas what could cause this? It seems odd that only office software is
affected and it works for other users so I assume some corruption in the
current user registry but why would system restore fail?