.Net Application - Post Back

Okay, now please do this. Modify your iRule to include some log statements and then test again and report your findings per browser. Make sure you follow the same actions in all of the browsers so that you can compare the results.

when HTTP_REQUEST {
    set uri [string tolower [HTTP::uri]]
    log local0. "User-Agent: [HTTP::header User-Agent]"
    log local0. "Requesting: [HTTP::host]$uri"
    if {$uri contains "departmentwebsite" || $uri contains "requestservice"} {
        log local0. "uri contains departmentwebsite or requestservice"
        pool Pool_Department
    } elseif {$uri contains "iisservices"} {
        log local0. "uri contains iisservices"
        pool Pool_IIS
    } elseif {$uri contains ".ida" || $uri contains ".exe" || $uri contains ".dll"} {
        log local0. "uri contains .ida or .exe or .dll - discarding"
        discard
    } else {
        log local0. "else condition"
        pool Pool_http
    }
}

It may also be useful to run a wire capture (WireShark) or browser capture (Fiddler) on the client side to see what the traffic looks like, what is being requested, and when it fails.