spanning tree issues between dell force 10 (RSTP) and cisco (Rapid PVST)

hi there,

ive hit a bit of a block when setting up spanning tree on a new set of force 10 switches. the F10's are set up to use rstp and that cant be changed as they're using VLT, and the cisco 2960's are using pvst. when i do a show spanning-tree on the cisco's the vlans are coming up as blocked (although vlan1 is forwarding). is there anything im missing to get this working? the cisco is set up as a trunk port and the dell is set up as a hybrid port with vlans tagged accordingly. ive looked online and it says that pvst should revert back to stp when this configuration is set however vlans are still being blocked.