first of all:
use bitmaps and not jpg or png.
second:
i think your slider ist to big or to small.

you mean the slider bitmap is too big or small, or the slider itself? Because i created it in the program Paint if that affects anything.

Not the bitmaps, the size its talking about is your sliders range.
Its either the MIN, MAX, or VAR values that are bad.

"min" MUST be zero or higher. Negatives not allowed.
"max" MUST be higher than "min"
"var" MUST be between, or equal to, either "min" or "max"