I have a new low-normal xt rear mech which is currently ghost shifting in certain gear combinations (14-44 seems to be the worst). anyway, its very annoying and dangerous because it could cause me to greviously injure my groin if the chain slips. has anyone any suggestions on how to fix this? i have played around with the adjuster on the back of the mech which works for a while but then it starts its old tricks again. it seems to be at its worst after a long, steep climb and then on the downhill its starts to shift in and out of about three different gears. any suggestions would be much appreciated as both my LBS's are worse than useless at anything other assembling kiddy's tricycles, they refused to touch my bike when i brought it in!