I'm running 3.0.8 f7 on Windows 7 64-bit.
When I run in the Unity editor everything looks fine. When I build for PC standalone, and run the build with any quality setting that has Anti-aliasing set to 2x or better, everything looks fine, but when using the default "Good" quality (or lower) all of my UISprites disappear (Good has Anti-aliasing set to Disabled by default).
Note that I just updated from Unity 4.3.1 to 4.3.3 this morning, but I don't know if this problem was happening before then since I didn't test outside the editor until after I did the Unity update.
Thanks for any help you can offer.