[Plugin: Custom Post Type Archives] is_post_type_archive Failing Sporadically

Hi There. I switched to using your code on the current site I’m building … thank you for your work … but wanted to let you know that the conditional for is_post_type_archive is failing on me sporadically.
I added in a function to flush the rewrite rules on activate and deactivate of the plugin, and have to do this in order to gain functionality of the conditional again … otherwise it just continues to fail and my sidebars that are meant to show up in the archive don’t get pulled in.
I have no idea what is causing this, but, thought you might be interested in taking a look to troubleshoot? If so, just let me know and I’ll give you a login to the site to take a look.
Figured I would try here before going ahead and just hard coding a different sidebar for those 😉