Menu 1 drop-down sub-menu styling

I am using Atahualpa 3.5.3 in WordPress 3.0. In my menu 1 (page menu) bar, the drop-down list background color does not fill and I get gray on top of white color. Depending on the length of the text in drop down menu - I get varying fill of grey color. I want it to all fill in grey... How can I do this?

Also, when my drop-down list items is are short names, two names appear in the same line - but I want to have each drop-down item show one per line...

Please provide me detailed instructions on how to fix this problem. Thanks in advance!