[Users] Problems attaching ISO Domain to second dc

Hi, I had one iso domain attached to a DC (nfs based). I had second DC (fc based) and wanted to share the same iso domain as above. When i tried to attach the same ISO domain to the fc dc, it failed and all the other storage domains (data and master, nfs based) present in the nfs dc, went down/inactive. for some time i could see the status as "Contend" ( dont remember if it was against the storage domains or dc overall) ISO storage domains (backed by nfs) should be able to be attached to more than 1 dc.. but it failed for me... what could be the reason ? thanx, deepak