Joy, Elizabeth, Jay, & others,
  Couldn't resist a comment about Lactinas not working at high(er) suction.
Just yesterday (Sun.) I had a client bring back a pump which she said
suddenly began behaving exactly as you describe.  She had replaced the
gasket on the plunger & double-checked all connections.  She had rented once
before long-term, (bought a new kit with this rental) so I knew she is
experienced with the pumps.  Nothing she did made any difference, so I
merely switched her out to a new pump.
  I have since checked out the pump she brought back, but so far I cannot
get the same response.  It's possible that the belt is slipping and that it
is an intermittent problem.  If the new (just out of the box) pump begins
acting the same way, I will consider her kit to be the problem.  Since the
mom called (she & family live 1 hr. away from me and were in town visiting)
and wanted to have me look at her pump & since she had left her kit at home,
it was just easier to switch pumps.  Besides, I couldn't do any "scientific"
evaluation without her kit!
  Medela's customer service folks told me a few years ago that moisture
inside the cylinder can cause uneven piston movement.  In that case, they
suggested taking piston, gasket, & cylinder apart, washing with dish
detergent, and drying carefully by hand & with a hair dryer.  Another
suggestion to help was to rub a little salad oil on the gasket to enable it
to glide instead of grab.  I think moisture can build up in the cylinder if
it is left in place on the pump for long periods of time, esp. if the pump
is carried to places of widely varying humidity.
  I ask you, how many med. supply rental stations would be "open" on
Sunday?!  What we lovers of bf do for needy mothers!
  I really appreciated all the wisdom of problem-solving w/ pumps in the
last few posts.
  BTW, I can't believe the coincidence of Janet's post about birth control
pills appearing in the same digest as my query.  Janet, I find it appalling
that this happens to mothers & the poor women are frantic, thinking it's all
their fault.  I keep telling mothers to go back to their drs and insist that
they submit info back to the drug companies.  (My husband works for a
company which handles monitoring & data processing of drug trials, and he
tells me that through this kind of feedback from physicians (official forms
being filled out & submitted), manufacturers get new information which
wasn't covered in original trials.)  Dr. Hale, are there other ways to get
this anecdotal info published somewhere?  Letters in journals, perhaps?
Sara Reuning in Bristol, TN