Rekordbox playing music at 2-4x speed!

No idea what's happening here. 

First time user of Rekordbox, figured I'd install it in advance of a weekend of gigs next weekend so I can try out USBs for the first time (over from Serato). 

Whenever I play music, it just ends up playing super fast. 

BPM info is correct, and the timer on the track is just counting up faster than it should. 

I tried playing with the sample rate in the preferences, which gave some weird behaviour. 

I cycled through the options, some sped the music up and some slowed it down a bit. ONly when I tried 44100Hz for the FOURTH time, did the music slow down to a reasonable speed. However, it was still 16% too fast. I did this by playing music for one minute according to the stopwatch on my phone and checking the timer on Rekordbox, and it said 1:10. 

Help, please!