'WindowsImageBackup' folder: can't copy & paste to external USB

I never had any problems with this in the past: whenever I make an image backup, I copy the whole folder to an external USB drive, in case of internal drive failure. On one of my Win7 x64 PCs this still works, but on the other I am now getting an error message when I try to copy and paste the folder. 90% of the large vhd file copies, then I get the error "The requested operation could not be completed due to a file system limitation". All the other files and folders copy across OK.

I am not trying to extract any data from the file, just copy it to an external drive. Why has this PC suddenly decided it won't allow it? I have tried copying the whole folder from the drive where it was created (shared drive) to another drive on the PC (not shared), and copying from one drive of the PC to another worked fine, no error messages: but I still can't copy more than c.90% of the vhd file from there to my USB drive (plenty of space on it).

I'd have thought a simple copy and paste exercise should be straightforward? As I say, it worked fine last time I tried to back up the image folder in this way. Is the fact that the drive on which the image folder is created by Windows is now shared (across my wifi network to other PCs in my house) the problem?

Thanks for any help,

Martin

You say you are copying to a flash drive? Do you have any other images on the drive and have you renamed them?

How large is the .vhd file?

Hello... yes, I use this external USB drive to store a number of system images, but in different folders of course. I haven't renamed them.. The vhd file is 31.5 GBs..

Martin