Crop image from vb.net

I assumed that cropping an image would be an extremely easy thing to do from .net. But no matter what I try I just cannot seem to get the thing to work.

The documentation is somewhat vague -

'The first parameter is an array of four coordinates that mark the portion remaining after cropping'

That could mean an array of four numbers, or it could mean an array of four arrays of two numbers (a coordinate after all consists of two numbers). the 'portion remaining after cropping' I take to mean 'the portion of the image designated to remain after cropping'.

Since the select function takes an array of coordinate arrays -- {{x1,y1}, y2, y2}, {x3,y3}, {x4, y4}} -- I had hoped crop would work the same way. No dice.

Next, I tried the really simple approach, assume that 'left, top, right, bottom' really mean just that. So, I plugged in perfectly reasonable values and ... no dice.

In every case, PS throws a dialog box saying ' Could not complete the command because the affected area is empty or does not overlap the canvas'.

Here is a code snippet:

        Dim PSDapp

        PSDapp = CreateObject("Photoshop.Application")

        Dim psarray As Object = {20, 20, 120, 120}

        Dim PSDcurrentDoc

        PSDapp.preferences.rulerUnits = 1

        PSDcurrentDoc = PSDapp.open("c:\cat.bmp")

        PSDapp.activeDocument = PSDapp.documents.item(1)

        PSDcurrentDoc.crop(psarray)

What is even more strange is that if I take the above code and port it to a script, it runs just fine. Can someone (anyone!) please please post a minimal working example of using the crop feature using COM (not scripting)?