I have just experienced my first incident of a main gear unlocking
during taxi.  It is momentary, on a cylinder with 450 hours on it and
heretofore performing without problem.  The gear pump eventually turns
on and relocks the gear.  
   I seem to recall a number of years ago someone experiencing a gear
collapse after getting such an indication.  After talking to John Wollen
who builds these for Lancair, I wonder if it might not be the low
pressure switch on the hydraulic pump, rather than a hydraulic cylinder
problem.  

Hollis Helms
Oak Hill, VA