OS hangs for 8 seconds for every hyperlink

My Windows XP Pro SP2 suffers from bizarre, consistent 8-second delays
whenever I try to:

* launch a registered application by clicking a document in windows
explorer
* launch a registered browser by clicking a link anywhere in Windows
* launch an application using a shell keyboard shortcut (the Ctrl+Alt+
[x] ones).

Always this delay, on top of whatever time it takes to launch the app
or perform the command. The OS keeps running, only the calling
application hangs.
I suppose it has to do something with OLE, COM or DDE, but need to
figure out the problem before trying to solve it! Any ideas?

Thanks!