Another way is to update the wind (or temperature as well, I think) in the Approach Performance page. This then recalculates the profile and the residual differences 'tend' to disappear. That's not to say it resets any position errors, as Mircoburst2002 suggested you may be experiencing, but if your aircraft are GPS equipped and are linked into the FMGS (and not just the EGPWS, as some of the older aircraft are), then there are a few other things and techniques you can do.
1. FD's off, AP off. Give it 5-10 seconds. FD's on, AP on, speed/hdg/alt knobs all push! (back to managed) = essentially, recalculates for the FD's coming back on.
2. Swap AP's. So, AP off then engage the other AP.
3. Check positions of the 3 IRS's and GPS (if fitted). If one is significantly out then flag up on aircraft tech log on ground and try not to use that IRS. Beware if it is IRS-1 that you suspect, that engaging APPR mode on the FCU and both AP's (CAT 3 DUAL), you 'could' get a map-shift effect. Either leave it with just AP-2 and APPR mode or fly a selected heading to intercept localiser/Non-Prec inbound track.
4. Don't do any FMGC resets in the air unless absolutely necessary. See FCOM 4.06 for details.
5. Some people will be tempted to do a position update over a beacon. Try to resist this as much as possible as this is NOT a very accurate way of doing it! The Cone of Confusion overhead will extend and remain in the cockpit for quite a while afterwards, especially if you've used the wrong beacon!!!
6. What Jonty and Last Ditch were saying is also good as it forces the FMGC to recalculate the descent profile. If you have any doubt over which FMGC is out, try going to TRK/FPA (rather than HDG/VS, but keep the AP mode still in fully managed) and seeing which side is showing a 2.5 degree descent. That is the one which is correct.
I agree with capt solipsist, that once in close proximity to an airfield, the differences 'should' disappear. Should, being the operative word. A quick recalc as described or fly selected heading to the localiser will keep you safe. Don't do anything drastic. It's not THAT bad...
Hope that helps.