WinXp Pro and Juno Platinum trouble

I don't know if this is the place to ask this question, but here goes. Juno Platinum will let me log on via DUN at first boot and everything is great. If I log off and disconnect from Juno Platinum, work awhile on something else, than decide to log back on, the modem dials out but I get an error 628 code, I figure I will wait a minute or 2 and try again with the same result.
I log out of XP Pro and log back in, same error.
I have to reboot the computer than I can log into Juno Platinum again with no trouble. Does this sound like an XP problem with DUN or a Juno Problem? Sending and receiving mail is never a problem, I can do that all day long. It only appears to affect Web connection.
What I have done so far is uninstalled and reinstalled Juno. Conferenced with Juno(might as well ask my dog) Platinum support. removed and reinstalled DUN in XP. Also have tried a dozen or so other phone numbers to check for local troubles, always with the same result. Any help with this issue would be greatly appreciated.