So far my experience has been to have the IT group setup a seperate vlan for the phones and make sure the Shoretel boot option 156
I was just going to say to use option 156 on both VLANs, but you already took care of it. Once the phones reconfigure the Ethernet card for the new VLAN, they will come back looking for a DHCP server on the new VLAN. Sometimes people that are using a Windows server for DHCP don't have the network configured properly to pass DHCP to the second VLAN, and the phones will just sit there looking for a DHCP server.
Also, you should consider adding option 004 for a time server so the phones can have the correct time on the display.