Upgraded my HP ProLiant N40L from Version 5.2-5592 update 4 to 5.2-5644 via DSM and system went into infinity boot-loop.
Upgraded XPEnoboot to 5.2-5644.1 with same boot-loop. Unplugged power and SATA to the SSD drive used for SSD-cache and the system came back online without boot-loop and all data intact.