Hi Anita,
      A couple of things you said set off questions. Have you received a
new shipment of blades with a possible lot number change? You mentioned you
had service on all your microtomes, the lubrication on our 1512's may be
different and I bet all the angles settings have been changed in the
cleaning process and need to be reset.
      Check your slide sections with a 40x objection and look for the wave
effect.( called "chatter" )  At this higher magnification, it should be
readily apparent that there is a  wavy  pattern and the thicker part of the
"wave" will absorb more stain and look darker. The harder the tissue the
more a problem is magnified.  Check for this "chatter" patern and give me a
call.
Don Birgerson
Leica microsystems
Technical Assistance Center
1-800-248-0123  ext 5918
7:00AM to 4:30PM CDT