That's a weird one. Normally with a clutch problem you can't disengage the clutch. I'm understanding you correctly you seem to have the opposite problem, meaning the plates are being held apart. I can't picture a mechanism that would do that. Did you totally miss your driveshaft when you reconnected the final drive? Did your clutch get bathed in oil, and now is slipping completely?
Here's simple one to check. Too much fluid in your master cylinder, causing the system to pressurize and hold the slave cylinder in the "disengaged" position.