Virtual box cannot clone, cannot resize

Hi all,

I copied some files into a shared (ubuntu/windows) folder which apparently excided my fixed hdd on the virtual box. After that i received the following error
Result Code: NS_ERROR_FAILURE (0x80004005).

After searching online the proposed solution was to clone the vdi, then resize the hd and create a new one. I tried cloning which gave me a

VBoxManage: error: Details: code VBOX_E_FILE_ERROR (0x80bb0004), component Medium, interface IMedium

assuming this is a size error i tried to resize but apparently i cannot since i am using fixed space... this is the error i am getting

VBoxManage: error: Resize hard disk operation for this format is not implemented yet!

i really dont know what to do next...

any help is really appreciated!