100 mW argon laser 'double spot' on sample stream?

Hi,

We have a Spectra Physics 100 mW (SP model 277-GA01) argon laser on our 
Vantage - installed in August of this past year.
Sometimes when we turn the laser on, a double spot appears on the sample 
stream.  Other times, e.g., the next day, there is only a very nice, 
tight single spot.  When the double spot appears, we check to make sure 
there are no air bubbles in the sheath fluid tubing.  Also, we take off 
the nozzle and check to make sure there's nothing in the opening.  No 
matter how the laser spot is focused using the beam focus knob or any of 
the other adjustments - X, Y, Z - the double spot won't go way.  And 
they aren't vertically aligned.  That is if you adjust the Y control 
knob, the two spots appear and disappear at different points - close but 
not one on top of the other.  And this occurs when none of the other 
lasers are turned on.

Has anyone else with this laser experienced something similar?

Thanks.

Ray Hester
Univ. of South Alabama
rhester@jaguar1.usouthal.edu