I can’t say for sure if this graphical glitch only happens in the Nimbus level, but it seems to occur on that level at least.
As you can see there are black squares. They show up for only a few frames when the melon pickup particle effects shows up, and they often flicker. It’s very noticeable. I had to record the game using Fraps and then use VirtualDub to be able to get the frames, trying to take screenshots manually was near impossible.
I never had this graphical issue before, it showed up for me after the 0.1.1.0 update.