We are not aware of this error and you are the first to report it. This is all I have found in the net regarding a possible HTTP error 12152:
The server has been taken down momentarily for database or server maintenance, or there has been a network error. Please try again later.
Transport Status 12152 means Connection Closed by Server.
From MS instead, I found the following for the WinHTTP component:
ERROR_WINHTTP_INVALID_SERVER_RESPONSE: The server response cannot be parsed.
I don't have much to add to it now. I would suggest you to try again the spellchecker on the problematic PCs and see whether the problem still persists. You can also search in Google for a solution for this problem.
Please let us know if you have any instructions on how to reproduce the problem on our side
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