Error when sending file — Error code 0x80040233

I have never seen this before until yesterday. I’m on 6.0. A friend is on 5.9. I’m trying to send him a file and no matter which method I use (drag and drop OR “send file”), I receive the following error:

“Error code 0x80040233 needs a message, please report this problem.”

Anyone have any clue what this means? I’ve rebooted. So has he. I’m able to send files to others (both on 5.9 and 6.0) without problem. What could be causing this?

Thanks!