A possible problem with task priorities

I often have applications running in the background that consume all the processor power on my Dual Athlon computer. I set their priority to something below Normal and do something else. This way it's hardly noticable that they are running at all; everything responsible and all. But. Since I installed TLB I noticed that it feels like the TLB task (which is not visible though the Task Manager) has some low priority, so once I have my CPU consuming tasks in the background running, TBL gets very unresponsive to clicks, displaying its animated icons and menu browsing. I've never had anything similar with the standart Explorer toolbars. Moreover, it feels like not only TLB gets unresponsive when low priority tasks are running, but also every app I launch through TLB gets the same lower priority. For example if I launch Outlook Express through a usual shortcut or just by clicking its icon in /Program Files/Outlook Express/ and then check e-mail, everythihg goes smooth and as expected. But if I launch OE by clicking on its TLB icon I created, Outlook becomes very slow at checking e-mail, with the progress window slowly popping up and visible redraw of stuff, as if Outlook shares the same priority with my background task, eventhough Task Manager shows OE has "Normal" priority.

I'm on Windows 2000 SP2 installed on a Dual Athlon 1800+ with 1 GB of RAM.