OS: Gentoo
gpg-agent (GnuPG) 2.0.16 or 2.0.15 (and possibly others)
libgcrypt 1.4.5
Arch: x86

ssh-add for a 4096 bit key behaves oddly on my x86 box. It prompts for the ssh
key's key, as expected. Then opens pinentry and prompts for the storage
password, as expected. From there, when the re-enter pinentry box should come
up, a pinentry box with a strength meter shows up. If you re-enter it there, a
normal renter box comes up with:
Invalid characters in PIN (try -805487941 of 1) and a new passphrase box.

On my amd64 box, this does not occur.

Please describe exactly what you are doing.