As it seems we had some major downtime. Thursday we decided to shutdown and export the vm's and then upgrade the hyper-v server from 2008R2 directly to 2012R2. I wat a joy that we had bringing the servers back online. All that could to wrong did go wrong. After a nice export in hyper-v manager 2008R2 we wiped the server and did a fresh install of 2012R2 hyper-v. Then we tried to import the servers well luckely for us it said... error nothing to import. After a quick search we created new virtual servers and hooked them with the existing vdh files. This gives us at least working machine but in the next days or weeks we will convert the gen1 vhd's to gen2. So more downtime expected :)