I'm using Windows XP Professional SP3. I'm using Outlook 2007 but the problem
also existed with Outlook 2003 (I just didn't bother checking for a solution
then but now that I've upgraded I want it working right). Whenever I click on
any Outlook icon - I have several including the one on the toolbar (or even
on the Outlook.exe file in the Office Folder in My Computer), I get an error
message:

Cannot start Microsoft Office Outlook. The command line argument is not
valid. Verify the switch you are using.

This happens with no other programs or other office programs. I can get in
only by typing the following in the run dialog box:

outlook /recycle

I've reinstalled outlook three times (both with 2003 and 2007) and that
hasn't fixed the problem. I've tried creating shortcut icons from scratch but
the same problem occurs. I think it's something in the registry but I don't
know where to look there. Does anyone have any ideas? I'm not even sure why
the run dialog works when the others don't.