How to disable panel cache for user menu?
Drupal has a lot of caching levels so you might need to "peel" each one off to know which level is caching the results. Since you're authenticated, it's not the page cache. And since you mentioned that you set the panel to "No Cache", then it's not the panel cache either.

You're probably facing the block cache here. You can either modify the block caching definition in code using hook_block_info_alter (see hook_block_info for the different caching levels), or use Block Cache Alter module to do that same thing via the admin interface.