15
Reassess your hiring practices and make sure that you select for team oriented employees.
Failing that, breath mints.
-Adam
I'd second muloh's question - what kinds of thing are they having problems with?
In my experience these problems are often (but not always) a sign of underlying problems with the team structure / skills / relationships that need to be addressed if you want to get the best out of everybody involved.
Is Mary not getting along with Fred because Fred doesn't know enough about how sane folk work with databases? Is Fred not getting along with Jo because Jo doesn't bathe quite as regularly as they ought? Is Jo not getting along with Mary because Mary is a rude SOB? If so you can almost guarantee that Fred, Jo & Mary are also annoying the rest of the team in similar ways.
Just coz one or two folk push the issue enough to avoid pairing doesn't mean the problems goes away. It may well be annoying other folk too - they may have alternate ways of coping. Like looking for alternate employment for example :-)
If the team doesn't work well together it isn't a team.
Out of curiosity - how long are your pairing sessions and how often do you switch pairs? I find that it's sometimes easier to deal with this sort of thing if folk are switching pairs on a regular basis - once or twice a day. That way everybody gets to share the relative pros and cons of everybody on the team - which can help everybody focus on solving some of the cons.