Since I reinstalled PT Real Drums have been out of sync. Changing the audio setting to 16 bit 44.1 cures the problem. Does that mean I can't record at any other setting if I want to put vocal tracks on?

Check for a box labeled Use 16 bit i/o in Audio prefs area, see if that makes any difference.

You said you re-installed. Did you have this issue previously?
Which version?
Are you generating new drums or are these on existing seq files?

More info always helps

that's weird.......changed audio preferences back and even at a different sampling rate and bit depth old real drum tracks are fine and new ones generate in sync......i'm puzzled but the problem has gone!

Glad you're back in the saddle. Sounds like a setting got corrupted and rewriting it worked.