Problem with gnome (mouse is locked in the bottom narrow area)

Every time I start my woody,it fisrt enters a graphic interface,I can see it is gnome1.4,but there is not typical menu of gnome,and I can hardly to move the mouse,I move and click my mouse randomly,and can see a menu of which in the top of the menu is debian,at the bottom is the menu exit(at this time I can use mouse but can not control it ,that is the cursor of mouse do move according to the move of the mouse) but I can not select the menu by mouse,The only way I can select menu is to use the key.After I select the submenu exit of exit,typicall gnome menu appear,A row menu lie at the top of the screen,But at this time,the mouse can not move,It is locked at the bottom narrow area.What is the problem.(When I use command xinit ,error says that "no screen found",but startx can work with the bad property of above saying)