Even without debounce the codes should work at least once. And if the Pronto detects them as RC6 (as it should) it would work better without debounce. There are multiple MCE codesets used by OEMs, so that's probably the issue (not sure how you would correct it).

I have one of those MCE IR keyboards, and there's so much stuff (lowercase, uppercase, numpad, ctrl+, alt+, etc) learning it all is a rather daunting prospect.