Just out of curiosity, if you first save the attachment, and then open it
from the folder to which it was saved, does it still behave the same way?
First thing I would try would be to clear out the temporary Internet files
folder. Please see here for instructions:
http://www.slipstick.com/outlook/securetemp.htm
Pay special attention to the fact you need to copy and paste the path into
the address bar or Start | Run because you cannot browse to this folder like
most others.
I need to also ask if you use an anti-virus scanner to scan incoming
messages. It may be worth it to try disabling any tie-in to Outlook through
the AV software's configuration and see if things behave differently.
Especially if these are password protected Excel files... I've experienced
issues where some AV software will choke because it can't scan the protected
file.
Another odd thing I've seen once or twice with Excel - sometimes an errant
reference to a previously opened spreadsheet causes Excel to choke. In
Excel, go to Tools | Options | General again. Clear the checkbox for the
recently used file list. Also, ensure the default file location points to a
valid path. If there is anything in the field labeled, "At startup, open all
files in:" clear that out.
And finally, I saw an Internet forum post out there that mentioned a faulty
printer connection causing a similar issue to this. I've never seen this
before, but it's worth a shot to check the printers installed on this
machine. Ensure whatever is there is available and can be printed to.
....any of this do anything for you?