Please verify you have the latest possible Patches installed on the MediaServer and make sure the scsitab-File got updated properly as well. That file can be a reason for Devices being incorrectly detected.
The "no devices found" Message can come from other Tools locking the Devices, like sanconf or Library&TapeTools (or the IBM equivalent).
Make sure none of them are open and active while you try to configure the Device, also check for hanging Processes.
You can also just copy-and-paste the Path to the Field without using the browse-feature.
You can manually modify the Device-Type in IDB using "omnidownload -device LogicalDevice -file FileName" and "omniupload -modify_device LogicalDevice -file FileName".