When I receive a message that contains a web link and click on it, I get
the message:

Windows cannot find 'c:\program files\maxthon\maxthon.exe" "%1'. Make
sure ...

Maxthon is my browser of choice and is the default browser (although the
GW client insists on using IE). The point is that the quotes in the
message appear to be mismatched, which would be internal to the IM client.

Any idea what's happening here? Just reinstall the IM client?