This issue has been reported by users on various Android support forums:
• Seems to affect Motorola devices on Exchange 2010
• Attachments also seems to be a cause
• Possibly has to do with original message not yet fully downloaded before Forwarded or Replied to
• The manufacturer and mobile providers recommend disabling SMARTFORWARDING (aka Auto Download Attachment) on the device. Some posts indicate that this doesn't fully resolve the problem
• Install a 3rd party email app like Touchdown. This appears to be the best fix.