Not only a german problem ;). We've had serious problems in Sweden as well. The biggest problem is that even though we have convinced our participants that there is no problem installing the software, their settings, firewalls etc simply won't let them.
We had less problems with Inquist 2.x when we conducted studies in 2006. This is is strange since Inquisit 3.x should have many more alternatives for installning. However it seems as if security (in Sweden) has increased a lot in a few years. I practice, few if any of our participants have been able to install Inquisit 3.x with any of the new features because they have been blocked for some reason.
The problems with Inquist 2.x was quite straightforward. A computer either worked or did not depending on whether the user had the rights to install activex. These new install metohods have, in our experience, instead introduced a lot of other problems with weird crashes etc. In practice, this has irritated our participants to a much higher extent.
However, Inquist 3.x webversion still is great to use in a lab and is flexibile enough given that someone with moderate computer skills will set up the computers.
It is really sad that the makers of viruses etc have forced people to have such tight security that they cannot install leigitmate software even when they want to!