Heyho
i think i just solved the problem when VMs turn black and do not respond anymore!
also they give most of the time this error: "Cannot open the disk 'path_to_virtual machine/virtual_disk.vmdk' or one of the snapshot disks it depends on" or similar errors.
Its most likely the case that you have many small ( 2GB) files instead of one Big file (10GB+) for your Virtual hard drive.
you can merge these files into one with the following command
"vmware-vdiskmanager.exe -r first.vmdk -t 0 merged.vmdk"
Since i merged my multiple files into 1 I dont run into this problem anymore also I got the feeling the VM runs overall more smooth!
Full tutorial can also be seen here:
dont forget to delete your old files and rename the new one like your old one ;)
I am sure not all people have this problem but I saw it quite often