What may be happening is when you start 33 different users at the same time, the SSL processing becomes overwhelmed and rejects some of the requests. The easiest way to do this is to stagger the start times for the virtual users. If you have 33 scripts with one user each, start 0 users, and then increment the time interval by one second for each group of test scripts.
For example, Script A starts at 1 second, script B at 1 second, and script C at 1 second - but scripts D through F start at 2 seconds, and so on. This should allow the SSL logic to successfully process all requests. Experiment with these numbers to see what works best for you.
In the real world, it is likely that your users will not all simultaneously attempt an SSL login - there will be some sort of delay even if it is just based on a person's reaction times.