Your plugin causes my site to crash

Hi, after approx. 3 days after installing your plugin our site crash. After investigating we can tell, that our site starts to run again if we deactivate your plugin.

I have looked for some installation guides and tried to follow them. I also did install Multi Currency, even if it is not clear if this mandatory or not (I do not have need for Multi Currency).

I have tried to install your plugin 3 times, with the same result. If it is possible to get it work, it would solve a nice feature to our site. If not, is it possible to a refund?