host header load-balancing

Can you try this :

when HTTP_REQUEST {
  switch -glob [HTTP::header value "User-Agent"] {
    "*MSIE 6*" -
    "*MSIE 7*" -
    "*MSIE 8*" {
    log local0. "[IP::client_addr]:[TCP::client_port]: Matched MSIE."
    pool site-10.130.14.98_9610
        if { ![string tolower [HTTP::uri]] equals "/login" }{
            HTTP::uri "/login"   
        }
    }
    default {
    log local0. "[IP::client_addr]:[TCP::client_port]: Matched default pool" 
      pool site-10.130.14.98_29710
    }
  }
}

I added a condition for your URI rewriting action.