strange nRF24L01+ behaviour

I have recently bought two nRF24L01+ modules (http://www.sparkfun.com/commerce/product_info.php?products_id=705). Both modules are connected to a Arduino board. I use this library to control the modules (http://www.mrroot.net/wp-content/uploads/2009/11/Mirf.zip) and an SPI library.

One board is acting strange: When I want to send some data from one Arduino to the other nothing happens but when I grab one of the module's wires it starts sending data (distorted). When I take my hand of the wire sending stops?

I already figured out this happens only with one board, the other board is working fine. The boards are totally new and never used before. I only soldered the headers one some time ago?

Could this be a ground or some kind of capacity problem? How can I check this?

Is there a way to check if I soldered the headers right? I soldered them according to a previous post (http://forum.sparkfun.com/viewtopic.php?f=13&t=21286)

I am already 2 days trying to get this working and I am totally lost.

Suggestions are highly appreciated :D