Cisco does have a Mac specific app called VPNClient that certain companies use... so yeah. I would concur with steveo's comment; if you rely on this app to log in to your company's VPN, it would be wise to hold off on installing Tiger for now.
After looking around the web for what seemed like forever, I found some hints of where the problem might lie... so I checked to see if the other user on my system had the same issue. Well, fortunately it didn't, and so I looked at the Keychain for that user and duplicated what was set up there...