Try setting windowed=true in your eqclient.ini and set the windowed resolution to something simple and in a 4:3 aspect ratio - like 1024x768. If you can get it running, then play with the display settings until you get something you can live with that still works.
Are you on Win11? There're a few threads with suggestions for issues with that version.
The wiki has some other things you can try - maybe one will be applicable:
https://wiki.project1999.com/Tech_Support
-Mcoy