tracks in player suddenly accelerate

0) Have you read the "READ ME FIRST" thread in its entirety before posting:  Yes, I have, I swear.

1) Operating System: Windows 7

2) OS Type: 64bit

3) Rekordbox version: 1.5.1

4) Using LINK: No

** 4a) LINK Connection method*: n/a

* 4b) Using with CDJs*: Yes (cdj-900)

**5) Hard drive / Flash drive / SD card file system: FAT16 FAT32 NTFS HFS+

* 5a) Does the device have multiple partitions*: No

* 5b) If it's a flash drive, is it a U3 device*: not flash

* 5c) With what utility did you format the device*: Windows 7 Starter (32-bit)

**6) Have you scanned your files for errors: No

**7) Have you scanned your drive for errors: No

**8) Is Rekordbox crashing at all: No

* 8a) If crashing, is it resulting in*: n/a

* 8b) If not crashing, are there any error messages*: No

**9) Are you able to repeat / reproduce the problem: Yes, it has been happening on and off for the last 2 hours.

* 9a) If yes, can you do it consistently*: No - it seems to be random : re-playing the same track it does not happen at the same points each time.

**10) Any other notes regarding your setup only*: I have all unnecessary devices disabled - ie., wireless adapter, CD-ROM drive, USB Camera and power management on all USB hubs is set so they cannot be automatically switched off

Provide as much detail of the issue here: It seems completely random to me - within the same 32-bar loop it will sometimes happen and sometimes not and when it does recur there seems to be no pattern. The audio output stops and the track appears to fast-forward for a number of bars - between 8 and 12 bars as far as I can tell.

Will check the hard drive but have been accessing audio files from it on 3 other audio applications without noticing anything unusual.

Very grateful for any advice you can give. I have only started using rekordbox since the upgrade to 1.5.1 so I can't say if this was an error on the initial install that came with my cdj.