Problem amtetcher SNF 2008-02-11 03:57:33: Observation of pumping problem

[masaharu at snf.stanford.edu]

On 2/10 midnight, I reported pumping problem.
Next day, I run the same sequence in the daytime, 
there was no problem.
Again, I did the same things in midnight, and I failed again!
According to the past logs, obviously, pumiping problems
oftern happen after 0 am, very late night (or early morning). 
And sometimes, next user used AMT in the daytime and 
said there was no pumping problem.
This is just my speculation but, is there, by chance,
causality between time of use (night or daytime) 
and pumping problem?