i also have idlerpg as a bot, but here is what i usually do for my bots:
i do go up on the server, register the nick, asks for the vhost, waits, get it, activate it.
then i quit, set up the bot to identify against nickserv then just connect it. and voila.
if the bot identifies well, the bot gets the vhost.
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also idlerpg have option to identify with nickserv.
did you set it up properly?
# (identify) command to send upon successful connect. if using a privmsg
# command, you must begin the text of the message with a ":" -- see below
botident PRIVMSG NickServ :identify <pwhere>
# command sent to recover nick if bot's primary nickname is in use if using a
# privmsg command, you must begin the text of the message with a ":" -- see
# below
botghostcmd PRIVMSG NickServ :ghost %botnick% <pwhere>
if you do a
/msg nickserv status <idlerpgbotnick>
what's the number which you get back ?
does the /whois of the bot shows that the bot is identified against nickserv?