Hi dnykolaishen, sorry to hear about this problem. If there is only one Firefox process in the Task Manager, something has gone wrong because Firefox normally will fire up three processes (at least) at startup.

Some security software may prevent this from working as designed, but the 73.0.1 update had patches to try to work around that. Separately, a recent Bitdefender update prevented Firefox from running, but I think that caused a visible crash dialog (and perhaps you don't run Bitdefender or you already updated it to get the fix for that).

If you check the Windows Event Viewer and look at the Applications log, are there events recorded for Firefox around the time that the startup process is stalling? Possibly those might provide further clues as to the source of the problem.

Thanks for your reply.

Not seeing events in Event Viewer that look connected to Firefox. An error that keeps recurring (with slightly different details) is the following:

Log Name: Application Source: ESENT Date: 2/22/2020 7:54:04 PM Event ID: 455 Task Category: Logging/Recovery Level: Error Keywords: Classic User: N/A Computer: DESKTOP-OCT5GHB Description: svchost (6072,R,98) TILEREPOSITORYS-1-5-18: Error -1023 (0xfffffc01) occurred while opening logfile C:\WINDOWS\system32\config\systemprofile\AppData\Local\TileDataLayer\Database\EDB.log. Event Xml: <Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event">

 <System>
   <Provider Name="ESENT" />
   <EventID Qualifiers="0">455</EventID>
   <Level>2</Level>
   <Task>3</Task>
   <Keywords>0x80000000000000</Keywords>
   <TimeCreated SystemTime="2020-02-23T01:54:04.578718900Z" />
   <EventRecordID>2626</EventRecordID>
   <Channel>Application</Channel>
   <Computer>DESKTOP-OCT5GHB</Computer>
   <Security />
 </System>
 <EventData>
   <Data>svchost</Data>
   <Data>6072,R,98</Data>
   <Data>TILEREPOSITORYS-1-5-18: </Data>
   <Data>C:\WINDOWS\system32\config\systemprofile\AppData\Local\TileDataLayer\Database\EDB.log</Data>
   <Data>-1023 (0xfffffc01)</Data>
 </EventData>

</Event>

I disabled my security software, but that did not help. All other applications on this computer seem to be working perfectly.

Check that Firefox isn't set to run as Administrator.

You can open the Properties of the Firefox desktop shortcut via the right-click context menu and check the "Compatibility" tab.

Make sure all items are deselected in the "Compatibility" tab of the Properties window.

• Privilege Level: "Run this program as Administrator" should not be selected
• "Run this program in compatibility mode for:" should not be selected

Also check the Properties of the firefox.exe program in the Firefox program folder.

You can try to uninstall Firefox and reinstall Firefox as a normal user.

• https://www.mozilla.org/en-US/firefox/all/#product-desktop-release

You can check that you do not run Firefox in compatibility mode. You can open the Properties of the Firefox desktop shortcut via the right-click context menu and check the "Compatibility" tab. Make sure that all items are deselected in the "Compatibility" tab of the Properties window.

Thanks, cor-el, this seems to have been the issue, since Firefox now runs. I'm curious about why running it as Administrator is a problem.