An http redirect irule that is executing but not actually redirecting

Thanks for sticking with this. Here's where I'm at currently.

If I use the irule below

when HTTP_REQUEST { if { [http::host] contains "xxx"} { HTTP::redirect "" } }

without a host header entry for the site, I get an immediate page cannot be displayed and a corresponding execution and failure in statistics for the rule on the F5 web UI.

If I add xxx as the host header (xxx as the host name in the bindings for All unassigned IPs or for the IP for the site), it takes a long while, then I get a paged cannot be displayed error, and no failure indicated in statistics (execution is indicated, but no failure).

With the rule disabled (not associated to the VIP):

I cannot load the page I'm trying to redirect to by hitting it directly if xxx is a host header (as defined above).

The only way I can load the page I'm trying to redirect to by hitting the url directly is if there is no host header (as defined above) and without this irule.

Any ideas?