Broke VM by expanding disk

I had a win 7 vm that was created and running on Workstation 9.0.1 build-894247 running on Windows 8 Ent x64 build 9200.

Today I expanded the hard drive from 80 to 160GB, and set it to 'persistent'. To my surprise the VM is now not booting: Failed to lock the file  Cannot open the disk 'D:\VMware_VMs\Windows 7 x64 - SAFE\Windows 7 x64 - SAFE.vmdk' or one of the snapshot disks it depends on.

Any idea what happened, and is there a way to revert the damage?

Thanks