[Plugin: Contact Form 7] File upload problem

I have 5 file upload fields in form, with limit of 500kb each. When form submited it freeze in process to return 404, but never get to the page.

I lower limits to 200kb each and it works same if there 5 images. Working properly only when every image under 100kb i.e. total is under 500kb.
If I try to upload one file over 200kb than instead of showing error message related to size overlimit, form freezes again.

Could you please help with solutions?

http://wordpress.org/extend/plugins/contact-form-7/