STOP 0x7b booting from iSCSI

I've a Windows 2008 SBS running. It boots of iSCSI. That setup worked for months until yesterday. I intended to reboot and gained a: STOP 0x0000007b INACCESSIBLE_BOOT_DEVICE and no idea why. My setup hasn't changed. No new controller, no new or changed iSCSI targets, no new Network Card or IP address changes. I had all Windows Updates on it. Last known good: same STOP. Allow unsigned drivers: same STOP. Safe mode (all variants): same STOP. Mount target from a client: works. Filesystem check fine. I booted of the SBS DVD but in computer repair options my target doesn't appear. When i choose setup the target appears. So, how can i diagnose what's going wrong? Any helpful tools? Any hints?

Thanks in advance

Michael

That STOP error code usually means Windows was unable to load a proper driver for the storage controller it needs to access the OS volume, so it just gives up booting as soon as it should be relying on its own device drivers instead of BIOS.

This can happen if the boot storage controller gets changed without informing the OS, as in physically changing it with a different make/model, or configuring it to appear to the OS as something different; it's a common error if you configure a SATA controller to emulate an IDE one, install Windows using it and then change it back to full SATA mode.

Maybe something was changed in the system BIOS or iSCSI card's config?