What messaging platform are you using? We have to use a propriety system built in-house by our parent company and have to add PERL code to every Outlook Conditional in order for the system to render them. Without the PERL, we get the same result as you indicated above.
If that's definitely not the issue, then the bulletproof solutions mentioned above SHOULD work. I'm finishing up a campaign that uses background images and live text right now and the only Outlook issue we're running into is with the 120 DPI clients (which we can't really do anything about... even with the Outlook pixel data added in the head of the email).
Yeah we probably should be using a width declaration anyway... EVEN with the marketing content ha.
Thanks for the suggestion! I'll start including this moving forward and see if the "hey I noticed..." emails trickle off, since I wasn't even able to replicate the issue in the first place! Thanks again :)