Never had this problem before.....

[filmdude100cms]

could just be poor inotation on the b, mine is that way, gotta tune it half tuned for 1 D chord, half for another.

[T714]

when people bring me their guitars complaining about a particular string not keeping tune, i look for two problems:

1st, intonation...hooking a guitar up to a Peterson Strobe Tuner allows me to determine the guitar's intonation and how far off it is. If it is too far out, I'll simply make a new saddle that custom fits that guitar's intonation.

To determine if its the intonation, simply tune your b string to pitch, then pluck a 12th fret harmonic on your b-string...if the light goes flat, the compensator needs to go forward...if your b-string is sharp, the compensator needs to go back...

2nd, tuners...i've never seen a low end guitar come with high-end tuners...so if this is a low-end guitar, replacing all of your tuners with good quality replacements (Schallers, Klusons, Waverlies, etc) is another option. When in doubt, though, refer back to the above