How to solve "File is not readable" Problem?

Good morning everyone,

Ive been experiencing the "File is not readable" error for long time right now. Actually im using Windows 7 and Adobe Illustrator CS 5.5.

And the curious is that the error is not constant, sometimes i try to open an file and it happens, and ten minutes later i open the same file and it works well.

I tried to search the problem everywhere, changing the color profile, reseting AI settings and etc. This error never happend on my MAC, only on Windows.

Anyone knows how to solve the problem?

Thanks in advance,

Kind Regards,