Loss of FMC's in flight 757/767

[FLCH]

Has any of you 757/767 pilots lost all of your FMC's just as you reach cruise altitude or shortly thereafter ? I have had three instances one in a 767 and two in the 757. All of a sudden the FMC's go blank, (on the 757 they go to the ACARS/FMC prompt and display Timeout). The windows above the EADI go blank (Except the autothrottle) The Autopilot stays engaged but all the information on the EADI ( except the pitch ladder)and Map Displays go away displaying only the lubber line . By the time you utter an expletive or two, things start to come back one at a time. I don't remeber the order, but the windows above the EADI show LNAV and VNAV PTH but they have lines thru them. It's back to normal after 6-7 seconds. I guess for me it's a case of "What the hell is it doing now ?? I dunno but I've seen it before." My apologies if this has been covered at length before. By the way our training department didn't have an answer.

[Charles Darwin]

Some of the low cost airlines use Windows XP home for their FMCs. My airline uses XP pro with excellent results.

No, seriously, are you using Pegasus or the old one? Pegasus does have all sorts of ghosts.

[stilton]

75/6/fmc

Yes I have seen this more than once, and ours are all Pegasus.

If the problem does not fix itself sometimes it is due to the zero fuel weight input in the fmc dropping out, upon which it bases all it's performance calculations.

Re-entering this should fix the problem, (I try to always write it down and keep it handy)

[FLCH]

Thanks for the reply...The 757's were Pegasus, the 767, was on the 400, and it was brand new back then, so maybe it was a software problem too...

[flash8]

On a related topic does your MEL allow for despatch with dual FMC failure?