Strange IE restriction on the number of external CSS

While developing the project I stumbled upon a strange bug in IE. Some styles simply did not apply to the page. Because the project is large and there are many styles; at the design stage, the CSS was split into many files for each logically separate block. Finding out the reason I, by experience, came to the conclusion that IE loads up to 31 external CSS files through. The remaining files are simply ignored.
Checked on IE6 and IE7.

Naturally, when the site goes into production, all the CSS will be in one file, but at the design stage this moment substituted the bandwagon.