[kh99]

Well, I was thinking that it may mean that the script is timing out, since there's a maximum time that a php script is allowed to run. But I just looked at the rssposter.php code and it already attempts to turn off the time limit. But apparently this won't work if your php is set up in "safe mode", and in that case, according to the php docs, there's nothing you can do to increase it.

Try going to Maintenance > View PHP Info and look at the values for safe_mode and max_execution_time.