I have to say that I'm using Qt 4.6.2 on Windows XP with SP3.

I've tried some other things too and if I put a small sleep (for 50 msecs for example) in my code, everything is OK. But puttings sleep aroung my code is not what I want.
I also found out that I start getting those timeout errors when "netstat -an" has about 4500 opened connection.