I'll try to be as concise and to the point as possible.
Previous version of Aquaria ran beautifully, no issues. But I was on a 7800GT at that point. I'm now on a Radeon HD 4850. I never played the game on the 4850 until after I'd uninstalled the old version and reinstalled the new. Unfortunately, I can't find a copy of the old setup file, so until I do this is strictly related to the new version (and I'm guessing it has something to do with my new video card, not the game itself)
So I got the 1.1.1 download and was pleased as punch, loaded the game up, all seems fine. Opening cinema is fine, new game is fine, first bits play fine, then I get to Home Waters and... something seems off. I'm not sure what exactly. I go into Naija's home, things seem fine again. Go back out... again, something isn't right. I take stock of the situation and the problem, as I can determine it, is as follows:
Basically, the foreground is jumpy and seems to be tearing as it renders. It's just kind of... jerky. I turn on FRAPS to check speeds (though it doesn't appear to be strictly related to framerate), and I'm getting about 150 frames or so in Naija's home, and about 70ish in Home Waters. I bounce out of the game, and try every combination I can think of at different resolutions with vsync on/off, framebuffer effects on/off, etc. No change with any of these combinations at 1280x1024, nor 1280x920, nor 1024x768. I update my video drivers to see if that helps as a new version came out on the 10th... install, reboot, and it doesn't help. Problem persists.
Now, here's where it gets weird. I go back into the game to test again, and I notice that Naija isn't tearing or acting jerky, nor are the game's backgrounds -- only the foreground environmental features and sprites.
Any ideas?