tasklist applet crashes with BadDrawable

[Stas Sergeev <stas_orel yahoo com>]

tasklist applet crashes in function tasklist_icon_check_x() when calling
gdk_image_get() (tasklist_icon.c:279). The error message is: 
Gdk-ERROR **: BadDrawable (invalid Pixmap or Window parameter)
serial 2081 error_code 9 request_code 63 minor_code 0.
It crashes when I start some programs, mostly X-ISP and it is very annoying.
I don't know much about programming for X, so can anyone please tell me why 
gdk_image_get() can fail with BadDrawable? The width and height parameters
are valid and the window parameter is always mask->user_data==0. What can
be wrong then?