Jennifer Avolio's dashboard

Hi, I've been trying to connect to my Basecamp service URL with the trial version of timepost. Each time I get this Error message:
"Timepost could not connect to Basecamp. Confirm your service details and try again."
I have tried this serveral times with the correct basecamp url and login info. Any ideas why it isn't working? I'm on a Dell Latitude D820 with Windows XP professional. My colleagues who are on Macs aren't having the same problem.