Microsoft says it’s investigating reports of a Blue Screen of Death with an “UNSUPPORTED_PROCESSOR” error message that’s been cropping up on some Windows 11 PCs after installing an update released earlier this week. The latest KB5029351 update includes the usual monthly fixes, but it appears to be causing issues when used with some MSI motherboards.

“We are presently investigating to determine if this is an issue caused by Microsoft. We will provide an update when more information is available,” reads a support note on Microsoft’s Windows health center.

I’ve personally experienced this issue on a Windows 11 gaming PC, which is running an Intel Core i9-13900KS on an MSI MPG Z690 Carbon WiFi motherboard. A number of Reddit users have reported the same BSOD after installing the update, all running Intel systems on MSI motherboards with the latest BIOS updates applied.

Thankfully, after experiencing the BSOD Windows 11 is able to recover and roll back the patch. Microsoft now appears to have pulled the KB5029351 update from affected systems, but it’s still available for everyone else. The update went through Microsoft’s usual Windows Insider testing, into the Release Preview ring, and then to retail copies of Windows 11 before issues were reported.

It’s not immediately clear what’s causing the problem, but it may well be linked to MSI’s recent BIOS updates in preparation for Intel’s upcoming 14th Gen desktop CPUs, codenamed Raptor Lake-S Refresh. MSI issued a round of BIOS updates recently for Z690 and Z790 motherboards that “support next-gen CPUs,” according to the patch notes. Reddit users are all on the most recent MSI BIOS update, and at least one reports that downgrading the BIOS update allowed the KB5029351 update to install.

We’ve reached out to MSI to comment on the BIOS updates and we’ll update this post with any response.