You could suffering from vmware-hostd hung problem. Go to ESX SC and restart mgmt-vmware service and make sure vmware-hostd services listening on all ports as listed below :
tcp 0 0 127.0.0.1:12001 0.0.0.0:* LISTEN 12548/vmware-hostd
tcp 0 0 0.0.0.0:80 0.0.0.0:* LISTEN 12548/vmware-hostd
tcp 0 0 127.0.0.1:8307 0.0.0.0:* LISTEN 12548/vmware-hostd
tcp 0 0 127.0.0.1:8309 0.0.0.0:* LISTEN 12548/vmware-hostd
tcp 0 0 0.0.0.0:443 0.0.0.0:* LISTEN 12548/vmware-hostd
Tested on all ESX 4.0 U1, U2, & 4.1 all using same ports. Sometime after restart, vmware-hostd will take time to listen on port 8307 & 8309. I have to wait till 10 minutes for ESX 4.0 U2 case before I can login via vSphere client .