Instruments Go Black

What did you do before this happened for the first time - did you install an add-on? Did you tweak anything in fs9?

No add-ons. My FS9 is out-of-box, nothing but a few downloaded aircraft. The 737 is the FS9 one.

INTERESTINGLY... This has only occurred on NORTHbound flights. I'm sure it's irrelevant, but true nonetheless....

What are your computer specs.
It could be a driver or a weak video card.

512 ram/ Radeon 9800 card

What these flights may have in common is that they all started parked at gates, with all power off... perhaps something about toggling the "Avionics" switch on the panel...?

I'm almost afraid to ask... but are you positive that you have switched on your engine's generators after startup? 🙄

Mind you that, if you are using custom panels, it may be that the designer slipped somewhere and did not correctly write the panel controls; It has happened to me that on a (payware!!) panel that the Gen switches did not function properly, even after switching them to "on" the gen's were not really enabled. Best way to check is to assign a keycombination to the "Generator/Alternator switch on/off" command, and use the keyboard to enable them.

Brook wrote:

512 ram/ Radeon 9800 card

What these flights may have in common is that they all started parked at gates, with all power off... perhaps something about toggling the "Avionics" switch on the panel...?

I don't know what your CPU is but I can guess that it's under 2 gigs.
Shut down slides, water, texture and shadows.
Turn down clouds and traffic and see if that helps.