Please provide more details of the problem.

Start Firefox in Safe Mode {web Link} by holding down the <Shift>
(Mac=Options) key, and then starting Firefox. A small dialog should appear. Click Start In Safe Mode (not Refresh).

Is the problem still there?

select options loaded very slowly.

select options ? What are you referring to?

the-edmeister said

select options loaded very slowly.

select options ? What are you referring to?

have a website where use <select><option></option></select> structure for load information. If load over 1000 options dropdown in open very slow after maybe 10 sec. this was this morning. but now is ok