Page redirect link unset between User is going to view a page and Content is going to be viewed rule sets

Hello Rules specialists,

I'm seeking some help to understand a strange behaviour.

I've developed new functionalities for a drupal6 site, using a lot of rule sets. It works fairly well on a local site running with wamp on my PC, but when I transfer what I've done and merge it with the existing site on the server, I get a weird behaviour.

Within my rule set for 'User is going to view a page', I issue a page redirect under certain circumstances.
No problem with my test site : Rules sets $_REQUEST['destination'] to the correct path, then the rule set for 'Content is going to be viewed' is run but does nothing special in that case, and finally I'm redirected toward the chosen path.
But on the production site, I systematically end up on the frontpage ! Tracking what happens with watchdog, I can see that $_REQUEST['destination'] is correctly set, but as soon as the rule set for 'Content is going to be viewed' is run, $_REQUEST['destination'] has been unset provoking the redirection toward the frontpage.

I did a lot of researches so far, but I'm unable to understand why $_REQUEST['destination'] is reset between the execution of the 2 rules sets.

The only workaround I can imagine is to force an immediate redirection, but I know it's not recommended as a good practice, and anyway if it works on my local site, I think it should work on the server.

Does anybody have some hints for me ?

Thanks in advance