I've had this problem for a while and I'm bypassing it by setting to manual incoming mail check. Since I bypassed it 2 weeks ago, I haven't had a crash since. I'm reposting it here, it might help others and me as well.
This post should help others who might have the same issue as I do. It would be cool if some of you would try to reproduce problem and report your findings? It should take less then 7 minutes if you can spare them.
I have a phone freezing issue upon receiving new email and I need help investigating it. For the duration of the test, disconnect USB and 3.5mm headphones cable.
1. Set a ring tone for incoming email, any ring tone. I use Ring_simplicity, preloaded on the phone.
2. Set send/receive mail check interval to 5 minutes (so you are finished faster)
3. After you set the mail interval to 5 minutes, just leave the phone "alone" and let the screen turn itself off or push the red button.
4. From the desktop, if you have multiple email accounts, email yourself a test message from one to another email account.
5. Once the phone checks for email and rings to notify you about incoming mail, don't do anything, just let it finish ringing and let the screen turn itself off, if it should come on during the notification.
6. Check to see if you can use the phone, if the screen turns on when you push the red button. If you get stuck here like I do, soft reset the phone and change the email notification settings and email checking interval back to your liking.
Any ROM version tests are welcome to confirm results.
Since you mention the market, I recommend downloading open market 1.1 app. It's a free alternative to the M$ market, few trials but mostly free apps and games.
Microsoft market place is badly done. In order to find something useful there, you really have to already know what you are looking for, defeating it's purpose. If you look at that app depository thread on XDA, I don't think any one of those (really useful) apps can be found in the market place.