We are also very new to ADSM and had simular problems when we where testing 
with a manual tape library.
The default mountretension=60 minutes we found is to low for our testing  
purposes. Tape ejects after 60 minutes of inactivity.
The volume status maybe to read only due to an error on the device. Make sure 
Windows NT native DLT driver or ADSMSCSI driver have started and not both of 
them trying to access the same device.
Either use the Windows NT driver as a generic pool or disable the native driver 
and start ADSMSCSI driver.

"have fun and don't lose your sense of humar"