Sorry to be the bearer of bad news. It's a browser issue - not a CSS or font file issue.
If you put Cyrillic text in the p
tag of that fiddle, you can see the font rendering Cyrillic text just fine (works with both the .eot
and .woff
files you supplied).
Internet Explorer (at least up to version 10) simply refuses to render certain font subsets for text inputs when using @font-face
.
I would also advise against using frameworks like cufón to solve this issue, since those will introduce a lot of usability issues when used on text fields.
There's not much we can do about this issue except for using a default font for these fields in Internet Explorer.