Recently, Resnet installed a new version of CCA which does the Operating System detection quite differently than the old, brain-dead use of the User-Agent string.
I described some issues here.
I have now figured out when the detection is done in this version (a bit technical): The OS is determined during the SSL negotiation phase of the HTTPS login request.
I have a work-around for people who use my Perl script to log into CCA on Windows. I'll keep the exact work-around private for now, since I don't want Resnet personnel (who are known to read these pages) to dissect it already ;)
So, shoot me an email (jfeise at feise dot com) if you want it.