lol yeah I had that too. Nasty problem, but you can fix it by clicking on the menu button over on the far right side of the app, it's the three parallel lines. Then click on "Customize." At the botton left of the screen there is a check box titled "Title Bar." If you select that, it should fix your issue. Worked for me anyway.

Good luck.

To fix this while still having tabs in the titlebar, I edited

C:\Program Files (x86)\Stardock\WindowBlinds\ff.css

and replaced the entire contents of the file with:

@namespace url(http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul);

#main-window {
  -moz-appearance: -moz-win-glass !important;
}

#titlebar-buttonbox > toolbarbutton {
  /* hide fake min-max-close */
  display: none !important;
}

#browser-panel > :not(toolbox) {
  /* don't needlessly apply blur on main content */
  -moz-appearance: -moz-win-exclude-glass; 
}

.tabbrowser-tab {
  /* makes text display properly, but there's probably a better way to achieve this */
  opacity: 0.98 !important; 
}

There's still a few issues with this (the tab opacity is very slightly below 100% otherwise the text would glitch out, and if you click the close button with more than one tab open there's sometimes a graphical error), but for the most part, this works well.

I am here but to serve