darren-mc wrote: This is a firmware issue. If I roll back to pre 3.3.3 then everything works fine. On 3.3.3 the router keeps loosing sync.

Depending on which firmware you upgraded from, this is probably down to the modem code, I recommend trying the 211801 modem code from this page:
http://draytek.com/user/SupportDownloadsDetail.php?action=Load&MID=12&ID=305
That would be the same modem code as older firmwares and might work better with your particular line.