Ok, actually it seems that the picture is somehow cropped at the top *and bottom* by appr 10 pixels. I saw a similar problem on one video in youtube (but cannot find it right now). So, someone else has also had the same problem. I'll try to find another version of the rom and/or neogeo bios.
*edit*
The actual version is Puzzle Bobble 2 / Bust-A-Move Again (1999 Neo-Geo) and this screenshot from mamedatabase shows exactly what I mean:
http://www.mamedb.com/snap/pbobbl2n.png The screen is cropped, e.g. the characters "stand" on nothing and there is nothing beyond the P1 sign.
I guess, I just switch to some aother version of this great classic
