How about something really crazy and unheard of?
I have two email accounts with Google Mail. Both are the only ones set up in the Mail app inside my iPad2. One would load everything: .jpeg, .docx, .pdf, and everything. The other would not.
I tried hard reset multiple times, deleting both email accounts and hard resetting. I cut all processes using SBSettings and killed all processes related to mail. So I have nothing running now, and I deleted all of the readers (Adobe Reader, Goodreader, Doc to Go, Quick Office), and other apps I had added.
Now I have nothing running and no apps installed.
Then I set up mail again from the bottom, as if the iPad came in the mail today. One gmail account still automatically opens and previews .jpg attachments, and show .doc, .pdf attachments with their respective icons. THE OTHER GMAIL ACCOUNT IN THE SAME iPAD MAIL APP DOES NOT OPEN THE SAME MESSAGES I HAVE FORWARDED TO BOTH. I would see an arrow pointed down in the icon inside that "faulty" mail account, and the name of the attachment below the icon. I have pressed my finger a gadzillion times on those icons, only to see the spinning wheel briefly and nothing. Holding them down would do nothing, and i can't open in other apps.
The wackiest thing is... when I hit forward (by tapping the curved arrow at the top), I get a drop-down choice list: "INCLUDE" and "DON'T INCLUDE" attachments. When I tap on INCLUDE, .jpg files immediately load and show in the reply message, only two of four .pdfs load and open, but no .docx attachments would.
How would we be supposed to troubleshoot or fix something like this?