I have had a couple of issues when using conditional formatting.
Firstly within a conditional format if I do not set the number format explicitly then the number formatting of the rest of the worksheet reverts to 'General'. This is easily solved by explicitly setting the format, but seems a little odd.
Secondly (and what I haven't solved) is that attempting to change the fill pattern on a cell within a conditional format always seems to result in a solid fill in black. This is what I have been using for the conditional format
A similar statement works for simple formatting. I would be grateful to know if I am doing something wrong.