Fixed cells - washing out fixative before running?

Hi all,

We've been having some problems with repeated (partial)clogging on  
our LSR-II and are working through possible causes and solutions.

One thing that has emerged in the past couple of days is that there  
is one group that runs fixed samples that are still sitting in the  
fixative (10% neutral buffered formalin), ie they don't wash the  
cells after fixing. There has been some suggestion that this might be  
contributing to the problem. Has anyone ever run into problems with  
people doing this? I've always washed cells after fixation and	
resuspended them in something else (like PBS) so I've not considered  
it before - it doesn't sound like it should create problems but I'm  
interested to hear from others.

Incidently, the same group is having a lot of problems running the  
same samples on an AMNIS Imagestream (the flow rate is unstable after  
the first couple of minutes) - could the presence of formalin also be  
an issue there?

Regards,

Adrian Smith
Centenary Institute, Sydney, Australia