Anthony is right - If you're using masking, avoid JPG format. The compression algo used means that pixels which were originally black, may not be *after* compression/decompression.
Try PNG instead. Good compression, no loss of quality.
If this isn't a blitz problem, how come areas that are totally black in paintshop pro, remain totally black in other apps such as paint, photoshop etc?
Nope. This example was made in Photoshop 6. The black circle was drawn with the hard-edged "pencil" tool. This is the result after saving as a JPG with minimum compression:Try PNG instead. Good compression, no loss of quality.
I need my files to be .jpg
Why? JPEG has no advantage over PNG...