e967af32cc5b9e7a91825877b65555a8 is the correct MD5 result for the 5.1.1 EN DVD ISO. 4,222,854.00 Kb in size, according to MD5Summer.

The mirrors are sometimes corrupt and I believe it may be in the way that the files are distributed. If you download a file before they have finished uploading them, it may be truncated.

I would strongly recommend the use of Bittorrent or equivalent torrent program for download. They are usually self correcting and verify the file as it is downloaded. It can usually repair a corrupt file if you save the downloading file to the same folder as the corrupt file. It can compare and repair the file, while downloading the parts it needs for completion. No need to delete what you already have if it's close.

Good Luck!