John -
Without knowing the intricacies of your environment, it's going to be difficult for anyone to give a you pinpointed answer to the problem you're having. Are you the only client experiencing this? No, not at all. We experienced the same this except ours problem was with PostMaster and not Management Reporter and ours was occurring overnight and not in the middle of the afternoon. However, I had to work with my IT Systems team for a couple of weeks before we finally figured out what the problem was. We've all given you enough information with which to get started down the troubleshooting process and as was suggested, if you're not able to locate the problem using the information we've provided, then you will need to open a support case with Microsoft.
Do you have a GP partner? Have you contacted them regarding this problem?
