As Dave said, check with another volt meter, (preferably a multi meter) If you can find one, The GT Power watt meter is the best tool you can have. It checks Amps, balances (shows individual cells while balancing or using as a volt meter in line etc. Hard to find but by far the most useful tool for batteries. Does LiPos , LiFe, and LiLo. Also does temp. You have to solder your own plugs on. This place may still have them, buy one while you can if they do
GT power still list them on their home site, but for some reason they are hard to find. They will do everything you need for battery checking. Some shops in UK still seem to advertise them.
A good charger is latest Sky RC IMax B6 Evo,
I've just bought one and they seem very good. Sky RC have been making chargers for years, - first charger I bought was a Sky RC ICharger and it's still working perfectly after 13yrs. The new one can have all your batteries and settings programmed in, (up to 10 batteries) so you don't have to re-set every time. Once you have them set, you just pick the battery and press start. Little bit tricky to get the hang of setting, but once you get the idea it's easy. Has alarms if you do something wrong, and stops itself (forget to put balance lead in, wrong cell count input etc) Quite idiot proof.
As Dave said, check you are not charging on the HV setting, - might be why you are getting a strange voltage. GT Power stuff is usually pretty good.
If you have a multi meter, you can test individual cell voltages by checking on the balance plug ie neg lead on meter to neg on plug, then test along the pos contacts (should give you voltages increasing by same amount) eg 3s charged would be - 4.2-8.4-12.6
Your charger should be ok, but it's good to be able to see the individual cells as it helps spot possible problems.