Hotspot login + http-keepalive = problem

I noticed a problem when i try enter a web site, be redirected to hotspot, login and then try enter the site. I get an error.

The problem is that while firefox sends this request

 GET / HTTP/1.1
 Host: www.terra.es

Mt proxy sends this to web server, which is imho incorrect:

 GET http://www.terra.es/ HTTP/1.0
 Host: www.terra.es

The problem remains until i close connection. The only way to do this is closing al browser windows because by it has http keepalive.

Tested on mt 2.9.38 with simple hotspot configuration, and FF 1.5 / IE 6.
Config:

/ ip proxy 
set enabled=yes port=8080 parent-proxy=127.0.0.1:3128 maximal-client-connecions=1000 maximal-server-connectons=1000 

/ ip web-proxy 
set enabled=yes src-address=0.0.0.0 port=3128 hostname="" transparent-proxy=yes parent-proxy=0.0.0.0:0 cache-administrator="webmaster" max-object-size=4096KiB cache-drive=system max-cache-size=none max-ram-cache-size=unlimited 
/ ip web-proxy access 
add dst-port=23-25 action=deny comment="block telnet & spam e-mail relaying" disabled=no 
/ ip web-proxy cache 
add url=":cgi-bin \\?" action=deny comment="don't cache dynamic http pages" disabled=no 

/ ip hotspot 
add name="hotspot1" interface=wireless profile=hsprof1 idle-timeout=5m keepalive-timeout=none disabled=no 
/ ip hotspot service-port 
set ftp ports=21 disabled=no 
/ ip hotspot profile 
add name="hsprof1" hotspot-address=192.168.222.1 dns-name="" html-directory=hotspot rate-limit="" http-proxy=0.0.0.0:0 smtp-server=0.0.0.0 login-by=cookie,http-chap http-cookie-lifetime=3d split-user-domain=no use-radius=no 
/ ip hotspot user 
add name="admin" password="" profile=default comment="" disabled=no 
/ ip hotspot user profile 
set default name="default" idle-timeout=none keepalive-timeout=2m status-autorefresh=1m shared-users=1 transparent-proxy=yes open-status-page=always advertise=no