We seem to have the identical issue with our EX4S servers running @hetzner.de equipped with an LSI MegaRAID SAS 9260-4i Raid Controller.
According to Hetzner the server is fully compatible with Esxi5.1.
The messages as per below appear in hourly intervals since installation date on multiple vmservers running Esxi5.1.
2013-02-01T12:59:35.943Z cpu2:6179)NMP: nmp_ThrottleLogForDevice:2319: Cmd 0x85 (0x41240079e1c0, 5231) to dev "naa.600605b005250ab018197c9f042e7aa9" on path "vmhba1:C2:T0:L0" Failed: H:0x0 D:0x2 P:0x0 Valid sense data: 0x5 0x20 0x0. Act:NONE
2013-02-01T12:59:35.943Z cpu2:6179)ScsiDeviceIO: 2316: Cmd(0x41240079e1c0) 0x85, CmdSN 0x408 from world 5231 to dev "naa.600605b005250ab018197c9f042e7aa9" failed H:0x0 D:0x2 P:0x0 Valid sense data: 0x5 0x20 0x0.
2013-02-01T12:59:35.943Z cpu2:6179)ScsiDeviceIO: 2316: Cmd(0x41240079e1c0) 0x4d, CmdSN 0x409 from world 5231 to dev "naa.600605b005250ab018197c9f042e7aa9" failed H:0x0 D:0x2 P:0x0 Valid sense data: 0x5 0x20 0x0.
2013-02-01T12:59:35.943Z cpu2:6179)ScsiDeviceIO: 2316: Cmd(0x41240079e1c0) 0x1a, CmdSN 0x40a from world 5231 to dev "naa.600605b005250ab018197c9f042e7aa9" failed H:0x0 D:0x2 P:0x0 Valid sense data: 0x5 0x24 0x0.
This implies D:0x2 (Device Check Condition), Sense Data 0x5 (Illegal request)
So this seems to confirm this to be an issue with this type of SAS controller and have logged a call with LSI support.
We had a mystery hardware hangup of one of our vmservers recently - hence the concern with these messages.