I am using web.show_document within Forms 10g. When I run my application from Windows Server 2003 the document called from web.show_document goes into the taskbar and blinks at me instead of opening, clicking the blinking application it opens fine. It doesn't happen when running from Windows XP. Basically I don't believe Forms gives up focus correctly.
This is a known issue. You will need to ensure that you are running 10.1.2.3. If you already are running patch 3 (10.1.2.3) then you may also need to install the Forms Bundle Patch (patch ID 9593176). For information about this patch refer to MOS Note 1188127.1