but would the missing semicolon make my IDE freeze up like that? (with multiple avr-g++, as.exe etc.. instances in task manager?
Not sure about the internal system stuff. I did mention that it didn't freeze up for me, but rather just gave compiler errors as one would expect. Possibly you have an underlining system problem in your specific installation/OS/ or whatever. Does you system compile and upload simple example sketches like blink?
Lefty