More info please.... Drag and drop what and where? Please provide steps and links to replicate the issue...

Is this about drag and drop between Firefox and another application or to the desktop?

Issues with dragging can happen if you run Firefox as administrator and made changes to the UAC settings.

• https://support.mozilla.org/en-US/kb/windows-administrator-launcher-process-error-fix

If this about dragging within Firefox then try Troubleshoot Mode.

• https://support.mozilla.org/en-US/kb/diagnose-firefox-issues-using-troubleshoot-mode
• https://support.mozilla.org/en-US/kb/troubleshoot-extensions-themes-to-fix-problems

In the case of my above reply with UAC dsiabled Firefox runs with medium-integrity in Windows Explorer that doesn't allow dragging to an application or target with a higher integrity.

I was trying to drag a income tax home page to the desktop

I was using a income tax program call OLT and had filled out some of it and wanted to save it to the desktop to finish it later and it would not drag and drop

to the desktop