Save your ssh-agent environment to a temp file so you can reload it in screen sessions/etc. that have the environment from a previous ssh session.

ssh-agent-fix

#!/bin/bash

SSH_AGENT_FIX_ENV_FILE="${SSH_AGENT_FIX_ENV_FILE:=$HOME/tmp/ssh-agent-env}"
SSH_AGENT_FIX_ENV_DIR=$( dirname ${SSH_AGENT_FIX_ENV_FILE} )

[[ -d ${SSH_AGENT_FIX_ENV_DIR} ]] || {
    mkdir -p $SSH_AGENT_FIX_ENV_DIR
}

env \
| grep SSH \
| sed "s/=/='/; s/$/'/" \
| tee $SSH_AGENT_FIX_ENV_FILE \
| sed "s/=.*//; s/^/export /" \
>> $SSH_AGENT_FIX_ENV_FILE

echo To set the SSH agent environment correctly, run the following in your screen session.
echo . "$SSH_AGENT_FIX_ENV_FILE"