The game runs very well on my PC and I've had no issues, other than slight stuttering.
I have noticed though that while flying over London if I shoot down a barrage balloon (it was just too tempting, even though I only fly RAF) the explosion causes the sim to freeze with the sound of the guns playing in a loop. I'm able to exit the aim by pressing Ctrl+Q then enter. I'm not sure whether this is a problem with my setup, but I've had no other issues with WOtR.

Just thought it best to see if others have experienced this? If not, then I'll just have to resist shooting at the barrage balloons.

Just tested pal..1st time no problems shooting 2 down,when i shot the 3rd i had a similar event to you.
2nd time i managed to shoot 5 down then WOTR exited to the debrief screen..Maybe its punishment for your treachery to the crown

Haha, maybe! It takes Balloon Command a while to get through to Sector Control on the field telephone.

I just tested this, shot down over 16 (or more lost count eventually) balloons over London no issues at all.

Check your sound card drivers, and video card drivers are fully up to date.
Try lower settings in WOTR if you still get problems, maybe memory issue who knows.

I'm running Nvidia btw.