Hi,
thank you very much for the answer. But this is a very new issue. We didn't encounter in the previous months, or last year. We switched to Office 2010 in March and after that we didn't have any issues at all actually. This problem just started, if I'm not mistaken, at the beginning of the summer. So I don't know what changed, but something has changed:)
I'll try the workaround and give feedback to you.
Thanks again.