Errors in startup script in Illustrator when Bridge is installed

Have managed to fix it - it's a Windows permissions error:

This is the technical fix for an "I/O error." You need to take ownership of the Startup Scripts CC folder and grant your user account full control.

Using File Explorer (GUI)

Navigate to C:\Program Files (x86)\Common Files\Adobe\.

Right-click the Startup Scripts CC folder and select Properties.

Go to the Security tab and click the Advanced button.

At the top, next to "Owner:", click the Change link.

In the "Enter the object name to select" box, type your Windows username. Click Check Names (it should underline your name) and click OK.

Check the box that says "Replace owner on subcontainers and objects."

Click Apply. You might see a few security pop-ups; just click Yes or OK.

After it has applied the new owner, click the Add button (on the same Advanced Security Settings window).

Click the "Select a principal" link at the top.

Type your username again, click Check Names, and click OK.

In the "Basic permissions" section, check the box for Full control.

Click OK, then OK again to close all windows.

Restart your computer and then try launching Illustrator.

(Don't be tempted to skip restarting.)

Illustrator is trying to read the file but your user account (or the application) is being denied permission at the file-system level.

This explains why it moves to the next file when you delete one; it's a folder-level access problem, not a file-specific one.