referral link is sometimes displayed incorrectly

Hi, I am using User Referral along with Userpoints, and I have an interesting new issue: the referral link is occasionally, not always, displayed wrong - as all 7's, e.g. www.site.com/referral/777777xx (where xx is something in hex code). When this happens, it seems to be the case for a few minutes for all users, and then it sorts itself out and goes back to displaying the right codes again. The all-7 codes do not work, i.e. do not result in storing the cookie, or in any case points are not awarded as they usually are when the correct codes are used.

I don't know what makes them reset to the proper codes, possibly a cron run? I sometimes have to log out and in again a few times before it gets set right again.

I confess I have mucked about in the code somewhat, transferring the call to userpoints to the login_toboggan module so that it is called when the new user validates, rather than immediately; however these were minor changes and they are working, and in any case I don't see why it would interfere with the referral module displaying the proper code on the user page, or (even more mysteriously) why it would do this only intermittently. However, I did not notice this happening before I installed the login_toboggan module. Possibly a conflict in there somewhere?

any suggestions? anyone seen this?
thanks in advance...