In case you've just recently noticed a major slowdown in opening Word, or obtaining Explorer's right-click menu, see the following refs:

Slashdot - Verisign Certificate Expiration Causes Multiple Problems

VeriSign Bulletin: Expiration of VeriSign Global Server ID Intermediate Root CA on 1/7/2004

Symantec - After January 7th your computer slows down and Microsoft Word and Excel will not start

Here's the quick fix, from Symantec:

Solution: To temporarily resolve this issue until a permanent solution can be found
1. Close all programs.
2. Start Internet Explorer.
3. Click Tools > Internet Options.
4. On the Advanced tab, scroll down through the list box to the Security section.
5. Deselect the "Check for publisher's certificate revocation" option as shown here:
6. Click OK and restart the computer.
This document will be updated when new information becomes available or a solution is found.

I just tried this, and it fixed the problem nicely. HTH.

Mike