Wierd Phono problem - what causes this?

Playing a couple records tonight, after a couple weeks not using my TT, the left channel is very bright and irritating sounding, and the right channel is not bad, but very rolled off on the high frequencies. They don't quite average out - the overall sound is harsh and aggressive. Plenty of bass from both channels. I am using a Dual 616Q TT, Adcom crosscoil HO MC cart, and JJtube phonostage, plugged into my DAC/Preamp. CDs sound fine, so it's not a problem with the DAC/Pre, amps, or speakers. It was sounding pretty good the last time I played it. The cartridge does not seem loose, and I don't se any obvious damage. Any suggestions?