We've not heard of other users suffering from the same symptoms. It would appear that something is not right with the translated symbols. To check on this open one of the symbol files in a text editor and look for the timestamp line, this line begins with |R. Make a note of the format. Then edit the symbol in the symbol editor to force a change, moving an object and putting it back to the original location will be enough. Save the symbol and check the timestamp in a text editor. Does the format look the same or different (is there a timestamp in the translated file?).
Next, update the symbol in the design and see if this clears the issue for this particular part. If it does, then you will need to update the timestamps on all your symbols to get round the problem. You could re-run the translation and see if this fixes it, or try this script http://communities.mentor.com/docs/DOC-3454 from the Automation Community.
Thanks for the suggestion. I'll let you know if that solves the problem.