There was a bug in 3.1.5 that caused suggestionbox to load its own copy of effects script. Two possible options:
1. Upgrade to 3.2.2
2. Use "hack": add <rich:suggestionbox height="1" width="1" rendered="false" /> just in the beginning of the page to force suggestionBox's outdated effects script to be loaded first.
Thanks for your reply.
The "hack" worked fine for us.
Unfortunately we can't use Java 5, so upgrading to 3.2.2 isn't an option.