I feel your pain, Ryan - I just went through a nightmare re-installing the plugins for CS5.5. A call to RG support would definitely help - they're quick and responsive and will help you troubleshoot. I assume you've looked here:
http://www.redgiantsoftware.com/support/general/downloading-installing/
As it turns out, the installers for my installation on the PC were hit or miss. Some of them showed up in CS5.5 (Photoshop, AE, PPro) and some didn't. I had to find them (search for folders with the plugin names - in my case they were all in one place), then cut an paste them into the /plug-ins folders for CS5.5, then they worked fine. A real headache, though, for a while. Good luck!
Joe Bourke
Owner/Creative Director
Bourke Media
http://www.bourkemedia.com
