Mail Links won't open

[Kate]

I've just recently upgraded to Leopard (not Snow Leopard) and everything was running smoothly then I did the most recent Leopard upgrade to 10.5.8 via Software Update. Now, when I first start the computer, my mail works fine, but if I put it to sleep and wake it up sometime later, when I click on a mail link, nothing happens.

If I reboot the problem goes away for a while.

I've repaired permissions, reinstalled the mail program and nothing seems to help.

Any suggestions would be appreciated.

Kate