MSTP Pending problem

[SimonHinge]

I am creating a MSTP pending config on our switch's and getting a error message, tried to Google the error to no avail.

Current config:

ins 1  vlans 1,3,5,7,9,11,13

ins 2  vlans 2,4,6,8,10,12,14

the pending config I am trying to setup is:

ins 1 vlans 1,3,5,7,9,11

ins 2 vlans 2,4,6,8,10,12,13,14

I issue the

"no spanning tree pending instance 1 vlan 13"

but when I issue

"spanning tree pending instance 2 vlan 13"

I get "Some or all listed VLANs already mapped to another MSTI"

but a "show spanning tree pending mst-config" shows that vlan 13 isn't in instance 1 any more.

Is this error because the 'live' config has vlan 13 in instance 1?

Simon