ReadyNAS Duo RND2000 v1 connection problems

I have a ReadyNAS Duo RND2000 v1 with two 500gig drives connected to a Dell Vostro 360 PC via a Virgin Media rpouter. They were bought new in 2012.

Everything was running fine until two weeks ago when one morning the drive didn't show on my Windows network.

RAIDar reported that it couldn't see any Netgear drive.

I remapped the drive and eventually managed to see the files (mostly Word text files and jpg images) but recent files (the most important) just showed 'access denied' in Windows security. Strangely, older files would open.

I've reset the NASdrive using the button on the rear when starting up using the blue front button, but no difference.

I couldn't access the drive's web page showing password updates and network info, but wa able to remotely with a laptop connected to the router by wifi. But reseting the passwords still didn't let me into the files.

I can see the NAS drive on the Windows network but cannot now get in using the default user name and password after resetting.

I've been backing up the drive to a USB drive regularly but failed to do so a monh or so ago, meaning I can't access recent material.

Help!