The first thing to check is that you are using the correct picture format for your region. I'm not sure what PAL or NTSC encoding Croatia uses, i'm afraid (anyone?!)
Once you have the correct picture format, if NONE of the presets for any region gives you a picture, but you CAN get pictures with a TV set and the same aerial, it'll just be a case of trial and error with the PLL i guess...

If none of the presets are of any use for Croatia, but someone out there has a list of PLL's for a Croatia region, i would be more than happy to add it into SuperTV...
(A new SuperTV version should be out this weekend, btw.)