A crash caused by panels.DLL indicates a bad gauge.
Determining which gauge is causing the crash is a process of elimination.
Start by backing up the panel.cfg.
Does the plane have a VC? If so, remove all of the [VCockpitnn] sections and test.
If it still crashes you can disable individual gauges by adding // to the beginning of the line...
go from...
gauge00=Cessna!ADF,545,86
...to...
//gauge00=Cessna!ADF,545,86
...to comment out any gauge.
I would remove all of the pop up Windows and first focus on the main panel.
Comment out half of the gauges and test.
If it still crashes comment out half of the remaining gauges and test.
If it doesn't crash, remove half of the comments and test.
Rinse and repeat.
When you identify the culprit, go back to your original panel.cfg and comment out that gauge and test. There may be more than one bad gauge.
You can then look for an alternative replacement gauge.
cheers,
Lane