Does your Samba-connected machine show the drive as the proper size (~1TB) for the shared drive?
Is it possible you are trying to store the file on the flash stick somehow (Samba mis-configured)?
Obviously you are "really connected" if you can copy a 100MB file. This wouldn't be the first time Windows has given a misleading error message.
I just installed Sqeeze an hour ago, and tested a 1GB Samba transfer, it worked, but my HDD is ext2.
I prefer NFS to Samba, for several reasons, but I don't know if W7 supports it out of the box, may depend on the version.