rservice wrote on Feb 2^nd, 2013 at 11:53am:

Check the folder C:\Users\Yourname\AppData\Roaming\Microsoft\FSX. Note Yourname will be your actual name. The fsx.cfg folder will be found by opening FSX.Open it with notepad and look for the [Trusted] section. It may be quite large.Delete all  the relevant entries,e.g. for the 707, and save it ,then reinstall the 707.The FSX program should then rebuild your fsx.cfg file.Hope this helps. Ron

If the gauges are not allowed to run, they can still be seen but don't do anything.
To remove the gauges altogether requires either removal of the gauges from FSX, by deletion or renaming their containing folder, or editing of the panel.cfg file.

I managed to achieve the same result as the OP by first saving a default flight using the 707 and then renaming the panel.cfg file to panelX.cfg, producing the same effect as deleting it or moving it from its correct location in FSX.
When I restarted, sure enough, there were no gauges or 2D panels.

I suspect this to be the cause of this particular error, if only out of academic interest, however it has been resolved in much the same way as buying a new car solves a punctured tyre on the old one.