I'm back into that one, as this really could indicate a problem.
Please check in BIOS if reactivation of the memory slot is possible.
If the problem persists, please check in iRMC (management chip onboard, provides a web interface with an error log, pls. see corresponding documentation on ServerBooks DVD that came with the system or on manuals.ts.fujitsu.com) whether an explanation for the issue can be found.
Finally, if all of the above fails, contact the vendor of the box (or the DIMM, if not identical) for support.