Yes, I´ll have a look into this.

Edit: I´ve resaved the bitmap with Irvan View and 256 colours (8-bit). Now it works. I´ll send you the bitmap via mail.

Thanks allot! Works perfectly!

Any idea how I can do it in Photoshop?

Its the same as in Irfan View, set Image mode to 8 bit, indexed colors.

Indexed colors...

Thanks.