You're welcome. Glad to help.
Correct the C1100 is not on the HCL but try this > Install 5.1 on one of the server and than update this one to 5.5. I think this should work.
Take also a look at this thread Install VMware ESXi 5.5.0 issue on HP ProLiant DL380p Gen8 they got similar problems with newer hardware.
Have you updated to servers to the newest available firmware?