Here's the code I'm using to open an image taken with the camera with the default gallery:
Dim i As Intent
i.Initialize(i.ACTION_VIEW, "mnt/sdcard/DCIM/Camera/IMG_20121027_205219.jpg")
Log("mnt/sdcard/DCIM/Camera/IMG_20121027_205219.jpg")
i.SetType("image/*")
StartActivity(i)
Log("error:"&I)
When I click the button, the gallery opens and then just force closes itself.