Happens to mine too, I thought maybe that some bottles I had cleaned better than others. Might be the last batch bottled too. Good point........... and I thought it was just me. Those voices are calling me again!
If you are running XP try a restore point to a known good date or try Spybot search and destroy. You can dl for free just do a google on spybot. Sometimes you have to run a couple of spywares to achieve the desired outcome. Or when all else fails its time for a reformat and reload.
Cheers
Brass bottle pressure cleaner. Screw them on to a tap fitting. Applies great pressure into a bottle and gets all the gunk moving. The wire activates the water when depressed