When adding a debug breakpoint it triggers perfectly fine the first time it's reached. However, once using "Resume program execution" to continue that breakpoint does not trigger again.
Disabling and re-enabling the breakpoint fixes it but of course that's kind of annoying and might not work in some cases (such as a breakpoint inside a loop).
To be sure it's not related to something with my application (such as threads), I tested it using this code (inside my application though):
for x in range(3):
print "meow %d" % x
The breakpoint was on the 2nd line and triggered only during the first iteration