I always declare font-weight: normal and font-style: normal in my @font-face declarations. I'm not sure if that has anything to do with leveling the playing field between browsers or not:
@font-face {
font-family: 'Avenir Heavy';
src: url(fonts/avenir-heavy.eot); /* IE9 & compatibility modes */
src: url(fonts/avenir-heavy.eot?) format('eot'), /* IE6-8 */
url(fonts/avenir-heavy.woff) format('woff'), /* Firefox, Opera */
url(fonts/avenir-heavy.ttf) format('opentype'), /* Chrome */
url(fonts/avenir-heavy.svg) format('svg'); /* Safari */
font-weight: normal;
font-style: normal;
}