This is a known bug for Pro Tools 5.3.1 for Windows XP. It may lead to a burst of full code (very loud) noise or a digital pop. Until this bug is fixed, you should not use Pro-52 on a track followed by a reverb plugin. This bug applies to only 88.2/96k sessions.

To work around the problem, bus the Pro-52 output (either by using a send on the Pro-52 track or the output assignment of the track) to another aux input that has the reverb plug-in. Not only does this configuration eliminate the problem, but it also gives you greater control of the wet vs. dry signal of the Pro-52 output in the final mix.