May have found the solution thanks to a post from deathsled @ xda.
If some apps stop working over 3g (youtube and pandora) then your proxy settings might have been returned to Sprint. Follow these instructions to set them back to working settings for Cricket:
Dial ##3282#
edit mode
enter 000000 ok
goto advanced
scroll to RTSP proxy address and HTTP PD proxy address and change them to 0.0.0.0
hit back twice and now try youtube it should work!
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