Dear Leyla,
Till now only VMware ESX version 3.5, 4.0, or 4.1, or ESXi version 4.1 is supported. Officailly it is not yet anouced or confirmed for virtualize support with VMware ESXi 5.0 and 5.1.
for more detail refer below
Symantec DLP v12.0 System Requirements and Compatibility Guide
http://www.symantec.com/docs/TECH207023