Qt Creator - Delay of whole GUI

[@nubis]

Hi guys,

i'm new to Qt but already a big fan of this library. I looked at some demonstrations and already played around with Qt Creator. However one thing kind of confuses me. While dragging control objects, using the scroll bar or just clicking somewhere in the user interface of Qt Creator I often have some delay till the desired action comes into place.
For example I want to place a button. While hovering the mouse pointer over the corresponding entry, left clicking and dragging to the working space the "button"-symbol doesn't immediately stay in place after the left mouse button is released - it kind of gets "attached" to the mouse pointer.
After a little while (meaning the delay) the control gets finally placed where I first released the mouse button and I can grab another one.

Any idea?