RAdmin already has a resume upload feature built directly into the client.
You'll notice, that if you try and re-upload a file that already exists, say 75%, that it will not try and re-upload/download what you've already uploaded/downloaded. RAdmin client will verify the integrity of the exisiting partial download/upload before continuing, however, this process is very fast and ensures that your upload/download will not be corrupt.
I was talking about FTP in v. 2.2, it don´t seem to resume uploads
This feature is already implemented in Radmin 2.2. If connection was lost during file transfer session, the beginning of the file will be written anyway. Re-connect, try to transfer the same file to the same location once again and select "Overwrite". Only the ending of the file will be transferred.