Have iPad 2 or new iPhone running iOS4. When checking e-mail for an Exchange type account, sometimes the e-mail is blank / empty. It could be the preview that is empty or it could be the message body that is blank/empty. Affects one or more e-mail accounts installed on the iPad or iPhone.
It is actually document on the Apple web site in a tech note.
The "solution" is a force quit of the mail application.
To force quit on an iPad:
1. Click the round Home button to return to the workspace home screen of icons.
2. Double click the round Home button to see a row of icons that are currently running.
3. Select and hold the Mail icon until the red minus symbol appears in the upper corner. Click the red minus to force quit the application.
4. Double click the route Home button to return to the workspace.
5. Click the Mail icon to start mail again.
To restart/reboot an iPhone:
1. Hold the Sleep/Wake button on the top edge of the iPhone / iPod Touch until the red slider appears.
2. Slide your finger with the red slider to turn it off.
3. Press and hold the Sleep/Wake button until the Apple logo is displayed.
After resetting, mail behaves properly until days, weeks, or a few months later, it happens again. It seems random. When it happens, just do the force quit again.
2012/03 We have also had clients report the same blank e-mail for the body of the message using an IMAP setup, as well. Force quit for iPad and phone restart did "fix" the issue.
2012/05 Issue has been around since fall of 2010. New iPad "3" (new iPad after iPad 2 is just iPad again) also displayed this issue for an IMAP account. iPhone "5X" w/ iOS5 also displayed issue with account Exchange type to Domino Traveler. Still not fixed.