Problem using look-ahead in httpd mod_rewrite

Issue

After migrating from Apache 1.3 on HPUX to Apache 2.2 on RHEL 5.4, mod_rewrite no longer works as per the documentation.

The  rewrite rule that looks like:
RewriteRule  ^/(.*)$   http://62.44.157.13/$1?user=%{LA-U:REMOTE_USER}&ip=%{REMOTE_ADDR} [P,QSA,L]

On Apache 1.3 the lookahead is done correctly, but on 2.2 the rewrite log looks like:

192.168.20.200 - - [24/Nov/2009:14:18:35 +0100] [62.44.158.58/sid#8bf9928][rid#8cc4958/initial\] (5) lookahead: path=/NewImages/TM_PETRIX-E_Foot_Forside.gif var=REMOTE_USER -> val=
192.168.20.200 - - [24/Nov/2009:14:18:35 +0100] [62.44.158.58/sid#8bf9928][rid#8cc4958/initial\] (2) rewrite '/NewImages/TM_PETRIX-E_Foot_Forside.gif' -> 'http://62.44.157.13/NewImages/TM_PETRIX-E_Foot_Forside.gif?user=&ip=192.168.20.200'
192.168.20.200 - - [24/Nov/2009:14:18:35 +0100] [62.44.158.58/sid#8bf9928][rid#8cc4958/initial\] (3) split uri=http://62.44.157.13/NewImages/TM_PETRIX-E_Foot_Forside.gif?user=&ip=192.168.20.200 -> uri=http://62.44.157.13/NewImages/TM_PETRIX-E_Foot_Forside.gif, args=user=&ip=192.168.20.200
192.168.20.200 - - [24/Nov/2009:14:18:35 +0100] [62.44.158.58/sid#8bf9928][rid#8cc4958/initial\] (2) forcing proxy-throughput with http://62.44.157.13/NewImages/TM_PETRIX-E_Foot_Forside.gif
192.168.20.200 - - [24/Nov/2009:14:18:35 +0100] [62.44.158.58/sid#8bf9928][rid#8cc4958/initial\] (1) go-ahead with proxy request proxy:http://62.44.157.13/NewImages/TM_PETRIX-E_Foot_Forside.gif [OK]