Hi,
I had the same problem with the C850 and did some tests today to locate it. I kept comparing our files with an (older, probably) original version of Hector Molina's panel, which worked almost well with the EHM aircraft.
I thought there is some (DLL?) version compatibility issue, and it still may be, but I eventually found out a shortcut that does the trick (for me, at least).
I noticed the problem is related to the virtual cockpit. That is, by installing the Eurobusiness kit THEN removing the virtual cockpit sections from PANEL.CFG I eliminated the problem along with it. As I almost never use 3D panel, for me it's problem solved. And it may help to find the real cause.
What bothers me is that at some point I got a configuration (of mixed files from the 2 kits) that worked with the EHM PANEL.CFG, but was unable to reproduce it later.
Hope this helps...
Andrei