I pasted an image into the card browser (as shown), causing a “Processing…” window to pop up. I waited for a while, got up from my computer, came back, and it was still “Processing…”. As of writing this, it is still processing.
At least it should tell the user what its processing…
Are you using an add-on? An add-on can choose to make a Processing… window to pop up while it’s doing a QueryOp. Try disabling add-ons one by one. This is one of the steps described in the troubleshooting page linked above.