Ah, just got it working again.
Before I just deleted the ~/.servoy folder, and the webstart cache and it didn’t work. But this time I delete those two folders plus the java ‘temporary internet files’ and now it is loading the solution again. Weird that it happened on all the machines around me at the same time as they are not running this version or from this server but it seems to work work now. shrug
Thanks for the helpful suggestions! Now back to updating my solution to 3.5