I haven't seen any other reports in this forum or the official Adobe feedback forum (http://feedback.photoshop.com/photoshop_family/products/photoshop_family_photoshop_lightro om) about general incompatibilities between LR 5.5-written metadata and other programs. Over the years, some incompatibilities have arisen, but they've generally not the fault of LR (that is, LR strictly adheres to industry standards).
Besides Third Light IMS, are there other programs you've observed not being able to read LR-written metadata?
Suggestion: Perhaps you could upload a sample problem pic to Dropbox (or similar) and post the link here. Then those of us experienced with LR metadata could take a look and test it out with other non-Adobe programs and perhaps narrow down the issue.
You could also try posting in the official Adobe feedback forum, which Adobe employees do read, though without more specific details about the incompatibility, I think it's unlikely Adobe will take any action.