ESXi 5.5 Unable to connect to a ESXI

I've lost connection to several ESXi 5.5.

First, I saw they lost connection with vCenter (5.5 SLES Appliance). Then I tried to connect directly to the ESXi using the vSphere Client, and got Error 503 The server could not interpret the client's request (Error on remote server (503) Server not found.) If I try to connect via HTTPS, I get the 503 error, too.

I've restarted management agents several times (GUI and CLI), but this didn't help. After that I ran ~ # services.sh restart and got this:

Starting ntpd
Running DCUI restart
Enabling DCUI login: runlevel =
VobUserLib_Init failed with -1
Running usbarbitrator restart
Errors:
Not all VMFS volumes were updated; the error encountered was 'Timeout'.
Errors:
Not all VMFS volumes were updated; the error encountered was 'Timeout'.
Errors:
Error while scanning interfaces, unable to continue. Error was Not all VMFS volumes were updated; the error encountered was 'Timeout'.

Googled that error, and ran ~ # esxcfg-scsidevs -l, but it seems to be always ok in there. Took a look to resolv.conf and /etc/hosts, and they seem to be ok, too.

It's suspicious, if I run df -h, it takes a long long time (and never ends).

Any info will be very appreciated.