we started experiencing the same thing with the extruding gels.
incidently we were using bio-rad reagents and this seemed plate specific.
we then switched reagents totally, to owls burst pak's (they make custom
4.25% gels) and have yet to experience any problems. washing our plates
in HCl didn't seem to help much. although to be honest i am not sure
what caused this problem, switching reagents did seem to be our cure (at
least for now).
good luck
-quan nguyen
glaxo wellcome
5 moore drive
rtp, nc 27709
quan_nguyen at glaxo.com