Ok, here's the scoop

I've got a yamaha FG403MS (here) and I love it, but recently I've noticed the top G B and e strings have been going out of tne for reasons unknown. The tuning knobs themself were slightly loose so I tightend them, but that didn't help. They've been doing this since the strings were first put on (6 months ago) at which time I just thought they needed time to stretch, but that hasn't really helped. I use a .6mm pick and don't strum overly hard, so I don't think I'm knocking them out myself either.

I'm by no means terribly smart at the hardware part of guitar, I just play (actually a bass player too), which is part of why I'm here asking the smart people... I hope.

Any suggestions or advice?

how quickly do the go out of tune? and i take it this happens everytime you retune them since the strings have been changed?
Quote by Renka
OddOneOut is an Essex S&M mistress and not a pirate or a computer program.

They go out of tune fairly quickly, sometimes before I start playing again, otherwise within a couple of minutes. Guaranteed out of tune within 10 minutes for sure. The previous set of strings was older than that and it didn't detune. The only reason I changed them is because I tuned to some alternate tuning but broke a string in the process. Possibly the brand of string i'm using?