If you tried to log in to CATS recently with a newly created certificate you probably failed. Especially when using a Class 3 certificate. Now I hope this bug is finally fixed.
Like usual for such bugs it was quite a trivial thing, for details compare CAcert/Education/CATS/login.php in svn with its previous version.
For analysis: certificates affected contained a serial number wich started with a non-digit character after stripping learing zeros. So Class 3 certificates with serial number bigger than 09:ff (issued since about half a year ago) and Class 1 certificates with serial greater than 09:ff:ff (issued since recently) have been affected.
I’m still waiting for the first explicit confirmation of someone now able to log in, but the analysis nicely fits the symtoms and the problem could be reproduced on the test system, so I hope we finally got it.