@LukeFF:
@DD, hmm, my German isn't too good. Google makes 'A call target has caused an exception' of it, but it doesn't make much sense to me. Does it happen with every file (dat/sim/etc)? Does it also happen when opening an sh(3).sdl file? Does it start loading (with the progress indicator) or does it immediately pop up this error...
Some more info would be helpful. Maybe you can send the file in question (in case of a heavily modded file). If that's not the case, and/or it also happens on stock files, then it is some other issue I am overlooking.
The weird part is I haven't really changed much in the department of loading a file. There may be a conflict if previous version didn't uninstall correctly, which can be resolved by removing the settings folder:
<Documents And Settings>\<user>\Local Settings\Application Data\skwas (<-- rename/remove folder)
In de mean time, do you still have a copy of v0.5.4?