"Having issues" is woefully vague, as it spans the gamut from "the moon has eaten my back yard" to "InDesign crashes when I go to File > Print but only if the document has an odd number of pages."
What happens? Any error messages or screenshots would be great, or a complete description of the behavior.
CS5.5 requires plugins that are specifically designed for it -- a CS5 version of QuickPrint won't work.
In 7.5.0 Adobe omitted this check -- 7.5.1 restores it. So an old plugin might have appeared to work in 7.5.0, but was likely a ticking timebomb waiting to happen.