Everything I play on my machine, whether it's sonar, soundcloud or internet radio is chipmunk...speeded up (not in a good way)
 
Any ideas?

Reboot everything, you're interface's clock has gone to potato. 

I wonder if the 424 might be defective.  This happens occasionally as well as distorted audio.  :(

I have had the same thing recently. Reboot is the way to go.

Are there any other devices connected to your interface?  Maybe something else has become the clock timing master.
 
 I have a AD/DA converter connected to S/PDIF of my audio interface, for example.  When i turn it on, it becomes the master clock, and sets the timing for everything.

Could be a problem with the 424 as you suggested. Speedy playback only happens to me when the MOTU is synced to ADAT at a higher rate than the project - i.e. 48kHz vs. 44.1, so just slightly higher pitch and speed. 2408 mkIIs are not capable of higher than 48kHz, so I'm not sure how you would get 'chipmunk' speed out of it unless the 424 is confused about what's connected. Maybe try re-seating the 424 card and re-plugging the Audiowire cable at both ends.