Agree with karthickvm
Sounds like a physical switch issue to me as well. Main reason - when VM is migrated via vMotion, one of the last steps of migration is that destination host sends out a request for a physical switch to update it's MAC tables (basically host is telling pSwitch that VMs MAC address will now be living on port attached to destination host). If you say that VM gets access to network after migration, seems that problem is resolved when MAC tables are updated on pSwitch.
I'd probably ask my network admin to take a look at pSwitch.
Other things to check:
Are all VMs affected or only some? If only some, are there any signs of MAC conflicts (like log entries on Guest, duplicate MAC errors on pSwitch) anywhere?
Which pNIC load balancing policy are you using? IP-Hash in some cases might show similar symptoms if pSwitches are not etherchannel capable.
WBR
Imants