Regarding the OP's setup: streaming from an airport external disk doesn't sound ideal. With computers, you want to keep in the "mainstream" sort of speak at least in my experience. You don't want to do these odd-man out setups unless you want headaches and hassles and maintenance.
I would ditch that setup. GEt a bigger drive for your MBP if you need it.
And check your wireless setup. N-only is better. 5ghz N-only is probably better yet.
Power cycle your ATV like others said to see if that helps.
Test with ethernet to eliminate wireless as a culprit. Wireless can be flakey which might account for the flakey problems some have with the ATV.
I would ditch that setup. GEt a bigger drive for your MBP if you need it.
And check your wireless setup. N-only is better. 5ghz N-only is probably better yet.
Power cycle your ATV like others said to see if that helps.
Test with ethernet to eliminate wireless as a culprit. Wireless can be flakey which might account for the flakey problems some have with the ATV.