Decryption problem - Large .png file

[Charly Avital]

Hi,

I have received from a friend a very large file in txt. that I have been
so far unable to decrypt:

[serial number].png.asc.txt. Size is 36.1 MB and it is supposed to be
the encryption of a 600 DPI color file.
Sender is running GnuPG v1.4.12 (GNU/Linux).
Because of the size of the file, sender has used Dropbox, and I received
it via my Dropbox.
I have tried to decrypt it using Terminal/CLI, with -d and -a options.
The output was gibberish, with bell sounds now and then.
After typing in Terminal gpg [return], I get the prompt "go ahead and
type your message". I copied/pasted the ASCII text, and at the end I
got: "gpg: CRC error; E9433F - B65688", instead of the expected
information about the keys the file had been encrypted to. Googling CRC
error etc., didn't bring several examples from this list (and others)
but nothing that I could use.
Sender is positive about having used my public key to encrypt the file.

Your help will be greatly appreciated.
Charly
0x15E4F2EA
Mac OS X 10.9.1 (13B42)
MacBook Intel C2Duo 2GHz 13-inch, Aluminum, Late 2008 .
(GnuPG/MacGPG2) 2.0.22 - gpg (GnuPG) 1.4.16
TB 24.2.0 Enigmail version 1.6 (20131006-1849)