Rather than go through an entire reinstall out the chute, try downloading (again) and reinstalling just the X3e patch. The X3e patch contains both the main SONAR program and QuadCurve EQ.

I just tried running the patch alone but have experienced the same problem. I am reinstalling X3 now. Crossing my fingers.

Thanks guys.

Joe

I just reinstalled X3 and then applied the patch and I am getting the exact same error window and the EQ settings are not saving. Also during the install I did not get an option about keeping my prior settings.

Anyone have any ideas?

Thanks again

Joe

If it's machine-specific, that's not my field of expertise. Before doing anything drastic, someone like scook might have an answer but lacking that, I suggest a call to tech support if installing the same software on two machines gives different results. 

Called out twice in one day. The last time was not so successful. Maybe this time will be different.
 
Before installing X3e again or whatever version of X3 you choose to install that has the QCEQ, delete or move out of the VST scan path "C:\Program Files\Cakewalk\Shared Utilities\Internal\PCS-GlossEQM.dll". This should insure the installer actually installs the new QCEQ. Also make sure there are no other copies of the PCS-GlossEQM.dll in the VST scan path.

scook - do you give stock tips, by any chance?

Not on this forum. I try to stay within the TOS.

This is copy and pasted from the Steam forums in which Seth answers a question from someone else who has experienced the same thing: 
 

First thing I would do is go to Edit > Preferences > File > VST Settings.
Change to 'Manual Scan' in the drop down under Scan Options.
Click, Rescan existing and rescan failed plug-ins.
Then click on the [Reset] button under Scan Options. 
Once the scan finishes, set it back to automatic from the drop down.
Then test again.

If the issue persists after this reset/rescan, I recommend you call our tech support line. They'll help walk you through some extra steps and tests to get your issue resolved. 
 

http://steamcommunity.com.../0/540739405879520376/

Right! Re-set and re-scan! Forgot all about that.

I am not sure reset and rescan will fix the
 
An older version of the QuadCurve EQ was detected. This may result in missing functionality and/or unpredictable behavior. It is recommended you reinstall SONAR.
 
message, if this is the error being received. When this has happened, it was the result of installing an older version of an X-series version of SONAR with ProChannel after X3 or a yet to be explained install error. For some reason, the older installer overwrites the PCS-GlossEQM.dll or the current installer fails to write the current PCS-GlossEQM.dll. It can also happen if a second older copy of PCS-GlossEQM.dll is in the VST scan path.