decrypt problem

[itsec.info]

Hi

I have encrypted a large file (280MB) with gpg v1.4.2 on suse 10.0.
By decrypting the file I get the following error message:

gpg: Problem reading source (10429120 bytes remaining)
gpg: handle plaintext failed: Dateilesefehler
gpg: Warnung: Verschlüsselte Botschaft ist manipuliert worden!

The last line is in German, basically it says that the text may be manipulated 
by a 3rd party.

Can I handle such huge files with gpg at all?
If so, what is the cause of this error because I am quite sure that the file 
had not been manipulated in the meantime.

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Any help is very much appreciated because this is a backup file.
Thanks,
Mike