It's quite easy to accidentally pass an image through a mask twice with PSP.  If you load a mask from an image's alpha channel, PSP will impose that mask on the layer *AS WELL AS* the already-existing alpha channel; unfortunately it won't use its own masks and alpha channels interchangeably.  So, if you only want the alpha channel to be applied to the image ONCE (otherwise the image will probably be a lot more transparent than you want), you must either delete the PSP mask or disable it (in the layers dialog) *BEFORE* saving the image as something like a .PNG, which supports a single alpha channel.
