You're doing indefinite loop, why you're surprised?

>Hi Gang!
>
>Here is a weird problem I ran across in an older application that I need to fix.
>
>In this POS app, there is a startup program call pos_strt.prg
>
>This is a bit of the code in pos_strt...
>
>

>_EXIT = .F.
>DO WHILE _EXIT = .F.
>	_EXIT = .T.
>	DO Mainpops WITH _EXIT
>*TMT 12/12/08
>ENDDO
>

>
>It's job is to create a system menu and wait until the user exits the menu, then loop back and create a brand new menu to use.... or to exit out.
>
>Here is the code in Mainpops.prg
>
>

>******************************************************
>*******************************************************************
>*  Description:  This program will create the POS menu that appears 
>*                at the top of the screen, it will also cycle back
>*                after every selection is completed.
>*******************************************************************
>PROCEDURE MAINPOPS
>PARAMETER _EXITPOS
>
>CLEAR
>
>*main_menu = "Main_Menu"
>SET SYSMENU TO 
>*SET SYSMENU automatic
>
>main_menu = "_mSysMenu"
>
>*DEFINE MENU &Main_Menu BAR AT LINE 1
>DEFINE MENU &Main_Menu
>
>DEFINE PAD _Cash_Reg  OF &Main_Menu PROMPT "\<Cash Register"
>DEFINE PAD _Inventory OF &Main_Menu PROMPT "\<Inventory"    
>DEFINE PAD _Utilities OF &Main_Menu PROMPT "\<Utilities"    
>DEFINE PAD _Exit      OF &Main_Menu PROMPT "E\<xit"         
>
>ON SELECTION PAD _Cash_Reg  OF &Main_Menu DO Regtemp
>ON PAD _Inventory OF &Main_Menu ACTIVATE POPUP Inventory
>ON PAD _Utilities OF &Main_Menu ACTIVATE POPUP Utilities
>ON SELECTION PAD _Exit      OF &Main_Menu RETURN
>
>*******************************************************************
>-SNIP-
>
>ACTIVATE MENU &Main_Menu
>
>_EXITPOS = .F.
>
>RETURN
>

>
>This is the Menu. If the user selects to exit, then a RETURN is done while _EXITPOS is still True, so the loop up above exits.
>
>Ok.... so far so good.
>
>If the app has the focus, then the CPU Usage is around 2 or 3 %.
>
>However, when a user switches away from the App to another application, the CPU usage of the App goes through the Roof !! around 98% !!!. For some reason, the Mainpops is not being done properly, and is being exited, and the loop in Pos_strt is running like crazy!!!
>
>Worse, if you minimize the App to the TaskBar, the same thing happens, but you CANNOT Maximize the app anymore!!!
>
>Weird....
>
>Any ideas????
>
>Thanks!