Testing levels on ST lvl editor erases all level's contents

[DatTuxBoi]

This happens with the latest nightly build.
Everytime I try to test a level everything (including manually-placed spawnpoint; i spawn on a specific random location) disappears. This includes blocks, points, badguys, everything.
When i exit the level and test the game on "extra levels" section, the game crashes. What can i do?
I tried to reinstall the game. Nothing happens. This doesn't happen with 0.6.0 and my computer isn't the only one with this problem.

[w_laenger]

Does this happen with every level?
If not, can you upload the level where it happens here?