Second menu under next div in IE7

My second menu under IE7 is hidden under the next div.

I have seen the FAQ with the position: relative problem, but I can't remove this because my theme(960 grid) is using this attribute.
The fix with z-index to 6 (or 1000) on ul.nice-menu li:hover doesn't change nothing.

My web site http://agency.3u4u.biz thanks to have a look. Click on "Print" to the bug.