Users working over the same database crash it. It seems that when users send requests in the same time, the DB crash (it can be fixed, but that's annoying). It doesn't always happen, but when you have more than 10 users, this increases the odds.

So the short term solution was Terminal Server. It worked great and speed was fine, until in some days something happened in the Windows Server that slowed it down (some kind of caching or somewhat), so the illiterate technician just said that Windows Server is bad.

We are now (Ok, I left) reckoning on an advanced/new Web or Desktop platform. They are aiming to finish a part in the software this year. Will see what they do ;)