Thanks. Disabled MTX, Plan G, over the network works as usual.
Enabled MTX, FSX sliders to 5%, Plan G freezes.
Sliders 1% ditto
Sliders 0%, PlanG ok.
Although there is some connection between MTX, and PlanG (at least over my network), I've found that FS Commander, over the same network, cares not a fig whether MTX is disabled, or with sliders set to 20%, MTX is working fully.
I think this enquiry should move to Plan G, rather than looking at MTX. For interest only then, I'm copying the event viewer message from my other computer.
Thanks for your help, Andy.
Edit: After typing this message, I tried V3 of Plan G (I was using V2.05, as I preferred it's map). Plan G V3 seems to like MTX, so my problem is solved!
C:\TA Software\Plan-G v2\PlanG.exe