“BAD signature” when trying to verify SHA256SUMS

when i try to verify the SHA256 sums of Ubuntu 14.04.3 LTS, i get "BAD signature".

I have tried to download SHA256SUMS and SHA256SUMS.gpg on в different network (just to be sure that isn't the problem) and gpg still says "BAD signature".

The fingerprint of the signing key i downloaded from в keyserver is: C598 6B4F 1257 FFA8 6632 CBA7 4618 1433 FBB7 5451

gpg's output when i try to verify the SHA256SUMS.gpg and SHA256SUMS:

$ gpg2 --verify SHA256SUMS.gpg SHA256SUMS
gpg: Signature made Thu 06 Aug 2015 07:45:46 PM UTC
gpg:                using DSA key 0x46181433FBB75451
gpg: BAD signature from "Ubuntu CD Image Automatic Signing Key  <cdimage@ubuntu.com>" [unknown]

gpg's verbose output when i try to verify the SHA256SUMS.gpg and SHA256SUMS:

$ gpg2 --verbose --verify SHA256SUMS.gpg SHA256SUMS 
Version: GnuPG v1.4.11 (GNU/Linux)
gpg: armor header: 
gpg: Signature made Thu 06 Aug 2015 07:45:46 PM UTC
gpg:                using DSA key 0x46181433FBB75451
gpg: using PGP trust model
gpg: BAD signature from "Ubuntu CD Image Automatic Signing Key <cdimage@ubuntu.com>" [unknown]
gpg: binary signature, digest algorithm SHA1

I really do not know what to do now, so any answer is appreciated.