Since last night I have exact the same problem!
System:
Joomla 1.5.26
CB 1.8.1
CB subs 2.0.2
I updated last week our website in a website-copy on a test-server (same environment/host). Everything was fine there. This night I installed the upgrade on the original website (with the latest CB & CB Subs files) and I have a problem with the registration-process and also the problem with [USERNAME]! After registration the CB Sub don´t create the subscription. The user get all email-messages correctly. But when he likes to login, he get the message, that he has no permission for this section.
Under this message he get the posibility to choose one subscription a second time. After this he can login.
The problem is, he choose in the original registration-form subscription A and can chose after trying to login only subscription B.
I´m looking now for hours, compare both installations in detail but I can´t find the problem.
It would be great, if you can take a look at this issue.