I haven’t run across this particular problem personally, but I thought I’d post it since I wasn’t able to find it documented anywhere else except on MSOutlook.info and in a few newsgroups.
It appears that the problem with opening Outlook attachments is due to a bug in Google Desktop Search (GDS) version 5.5.0709.30344 released on October 2, 2007. It was fixed in version 5.6.0711.24354 released on December 6, 2007.
Uninstalling the old GDS and installing the updated version fixes the problem. You can also try the following, which I found in a newsgroup:
“After performing the following steps, I was able to open attachments
in Outlook without completely uninstalling Google Desktop:
– In Outlook 2007, go to “Tools” > “Trust Center”
– Click “Add-ins” on the left-hand side of the resulting window
– In the lower part of the window, change “Manage: COM Add-ins” to
“Manage: Exchange Client Extensions”
– Click “Go…”
– Uncheck the “Google Desktop Search Outlook Add-in” then click “OK”
This leaves the Google Search Outlook toolbar available, so you can
continue to use it to search for messages. The only downside is new
messages won’t be indexed until you turn this add-in back on. So I
just temporarily disable it on the rare occasions when I have to open
a forwarded message.”