I might have similar problem, but unfortunatelly I don’t know the solution ;o)
If I insert [singlepic id=1528 w=320 h=240 mode=watermark float=] the picture works ok, but if I change the w and h of the picture the picture is not displayed on the page (same behavior as you describe).
I need to be able to change the w and h of the picture as not always it’s feasible to have the default values used. And right now it seems I may use the singlepic only with default values.
I seem to have similar problem and I don’t know how to solve it.
If I insert [singlepic id=1528 w=320 h=240 mode=watermark float=] the picture works ok, but if I change the w and h of the picture the picture is not displayed on the page.
I need to be able to change the w and h of the picture as not always it’s feasible to have the default values used. And right now it seems I may use the singlepic only with default values. Is there some solution for this?