Help~~!!! Microwindows Text using GrText() disapear

My project is using Microwindows for the UI part now. But recently i met a really trick problem.

My project's original design is displaying the screen to be horizontal. But now we are going to develp a new feture that can display the screen also as vertical.

So i use the GrSetPortraitraitMode() API, which like beblow:

    
if (!strCustomer.u8DisplayStyle) {
        GrSetPortraitMode(MWPORTRAIT_NONE);
    } else {
        GrSetPortraitMode(MWPORTRAIT_LEFT);
    }

But the result shows the screen indeed truns to be vertical, but all the text disappear. we always use GrText() to draw these text string, but none of them show up. That is so weird. I don't even find a way to debug this problem.

Did anyone meet this problem before? Any ideas will be appreciated.

(BTW, I am very new here, don't know if i post this thread at the right place, just search any kind of help as i can, this problem is killing me, LOL)