Need solution to show the listgrid in front

I am new to gwt and need help in fixing this issue. I have my screen with 4 subtabs. Each tab loads the records using listgrid. once i right click and select add,edit,view options it should show the form view of the tab class. The tab's form is coming but it's hiding behind the main screen. Please see the code sample

if(displaySpecialProgram== 1){
specialproggrid = new GridWithCallback(ConstantVars.memberSpecialPrograms,new MemberSpecialProgramsDS(),"Special Programs",ConstantVars.memberSpecialPrograms){

@Override
public void setupForm() {
wnd.setIsModal(true);
wnd.setKeepInParentRect(true);
}

@Override
public void setGridFields() {

}

@Override
public boolean isEditable(Record r) {

return true;
}

@Override
public void onSave() {

MemberProfile.getInstance().getWindow().show();
MemberProfile.getInstance().getspclProgGrid().getGrid().invalidateCache();
}

@Override
public void onCancel() {

MemberProfile.getInstance().getWindow().show();
}

@Override
public void onGridEdit() {

if(SystemClientUtils.getIntegerSysVariable(SystemVariableConstants.HIDE_MEMBER_PROFILE_SPECIAL_PROGRAM)!=0)
MemberProfile.getInstance().getWindow().hide();
}

@Override
public void onGridAdd() {
if(SystemClientUtils.getIntegerSysVariable(SystemVariableConstants.HIDE_MEMBER_PROFILE_SPECIAL_PROGRAM)!=0)
MemberProfile.getInstance().getWindow().hide();
}

};
childList.add(specialproggrid);
specialProgamTab.setPane(specialproggrid);
tSet.addTab(specialProgamTab);
}


in the gridcallback class i have some code like this

@Override
protected void onAdd() {
if (SharedUtils.nonMedhokMemberOnly) {
SC.say("Cannot Add/Edit. View only mode");
return;
}
if (canAdd()) {
if (criteria.containsKey(attributeName) && !criteria.get(attributeName).equals("0")) {
viewOnly = false;
saveButton.setDisabled(false);
getForm().clearErrors(true);
getForm().editNewRecord(criteria);
onGridAdd();
showWindow();
}
}
}


private void showWindow() {
getWindow().show();
if(buttonBar == null){
buttonBar = new HLayout();
buttonBar.setWidth(getWindow().getWidth());
buttonBar.setHeight(30);
buttonBar.addMember(saveButton);
saveButton.setAlign(Alignment.CENTER);
buttonBar.addMember(cancelButton);
buttonBar.setAlign(Alignment.CENTER);
buttonBar.setParentElement(wnd);
if(c != null){
canvasLayout.addMember(buttonBar);
}else{
wnd.addItem(buttonBar);
}
}
wnd.bringToFront();
}

but still the specialprgtab form is going behind and i have to close the main screen to see it. how can i fix this issue. please send me a response asap