I am also getting the "null" message:
checkDock/message chrome://firegpg/content/Webmails/Gmail/cgmail2.js 594 boutonboxs[j].getAttribute("class") is null
I am running Firefox 3.6.3 on Windows XP SP3, and FireGPG 0.7.10.
If I highlight the encrypted part of a message and use the right-click context menu to have FireGPG decrypt it, I get something like the following:
Decryption failed. Unknown error.
gpg: WARNING: "--no-use-agent" is an obsolete option - it has no effect
gpg: invalid radix64 character 3A skipped
gpg: invalid radix64 character 2E skipped
gpg: invalid radix64 character 2E skipped
gpg: invalid radix64 character 28 skipped
gpg: invalid radix64 character 29 skipped
gpg: invalid radix64 character 3A skipped
gpg: invalid radix64 character 2D skipped
gpg: invalid radix64 character 3A skipped
gpg: invalid radix64 character 2E skipped
gpg: invalid radix64 character 2E skipped
gpg: [don't know]: invalid packet (ctb=55)
gpg: no valid OpenPGP data found.
[GNUPG:] NODATA 1
I do know that the message is valid, because I can save it to a file and decrypt/verify it from gpg on the command line.
My GPG version is:
C:\WINDOWS>"C:\Program Files\GNU\GnuPG\pub\gpg.exe" --version
gpg (GnuPG) 2.0.12 (Gpg4win 2.0.1)
libgcrypt 1.4.4
Copyright (C) 2009 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.Home: C:/Documents and Settings/eroode/Application Data/gnupg
Supported algorithms:
Pubkey: RSA, ELG, DSA
Cipher: 3DES, CAST5, BLOWFISH, AES, AES192, AES256, TWOFISH, CAMELLIA128,
CAMELLIA192, CAMELLIA256
Hash: MD5, SHA1, RIPEMD160, SHA256, SHA384, SHA512, SHA224
Compression: Uncompressed, ZIP, ZLIB, BZIP2
I hope this information is helpful in solving the problem. If I can provide any further information, I would be glad to help.