I was about to upgrade my powerbook to Tiger but luckily found some reports indicating that Checkpoint's SecureClient (like most third-party VPN software it seems) does not work yet under Tiger.

Although I coulnd't find official info on the checkpoint website, the above report indicates that they should have a fix within a few days or weeks. I'll postpone my upgrade then.

Update: this eweek article seems to indicate that Apple is working with VPN vendors to solve the issues, but I've been unable to find updated news from Checkpoint. I've written them to ask for info.