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When I open a new document in Adobe, the whole workspace is covered in a pattern of tiny dots.

My workspace after creating a new document. When I open existing documents, this strange pattern is on top of the existing document.
This is affecting both new documents and opening existing ones.
I have updated Adobe Illustrator to the most recent version.
On my monitor the art board looks red and the workspace appears green. The windows and tools and surrounding borders of the program appear unaffected.
