From Frank J.'s X51v blog:

It seems a good idea to help Microsoft reporting the error that we are getting in the daily use of our devices with Windows Mobile 5 but… That slows down our devices up to the point that it’s almost impossible to use them. And this issue is currently worse due to the fact that many programs have not been converted or properly tested in this new OS.

So… If you want your Pocket PC running faster just disable this feature going to Start/Settings/System/Error Reporting/Disable and pressing OK. I did it as soon as I got my x51v and believe me; my device is running a lot better.