This bug occurs when the game cannot create a bitmap for "Block" and "Planet" items. The ways this error could have been triggered are:
1.) You made a planet or block with more than 16 million pixels in it (this probably isn't the case)
2.) The Flash-Player runtime was unable to allocate enough memory to create the bitmap
1) new pixel limit is 256 million (16,000x16,000). so this is definitely will not be an issue
2) maybe (?) depends on the system you have. I profiled a few levels and got a baseline of 100MB of RAM consumed. I guess it is possible to make a level so massive that it doesn't fit in RAM. For example, the previously stated theoretical gigaplanet is 1GB (16,000*16,000[pixels]/1,000[Kb]/1,000[Mb]/4[Bytes per pixel]).
There's not much I can do to fix this at the moment (except force the game to free memory before a level loads. Which would only prolong the error).
You might be able to do this. You CAN do this in the current build using scripts. However we might blacklist that command.