We've heard of this issue once or twice before, but it's not common. Can you tell me what caching you disabled? Was it the caching in the SCLogin module, or the Global Configuration caching setting?
Any information you can provide as to your caching config would be great to have so we can test and narrow down how caching would be causing problems. We do test with caching and it *should* work, but obviously, it seems like we're missing something.
Thanks,
Alex