Hi suneee,
Can you let us know what kind of the error do you have while trying to mount a virtual disk.
Have a look into the following KB's:
PGP Virtual Disk is Corrupted
http://www.symantec.com/docs/TECH177018
BUG REPORT: Mount of PGP Virtual Disk during logon is failed with "bad parameters" error
http://www.symantec.com/docs/TECH213547
I would also make sure that I have got the most recent backup of the keypair. If you see that private key has got a 0 bit size so most probably it was not successfully backup so you might have a problem accessing the drive if User Access to this drive was done with "Add User Key" and this key is in fact the one needed.
1.Do you know if you had more than one User added to the disk so potentialy you could try another user.
2.Did you try to add "New Passphrase User" as well.
3.Did you try to backup your virtual disk *.pgd file
4.Did you try to upgrade your PGP Desktop to the most recent version (SED 10.3.2 MP2) and try mounting the dive.