Problem importing CSV

Hi everybody

Can anybody shed some light on an issue i am having.
I am trying to import a CSV file with my products.
However it keeps hanging during the final step of importing.
I can keep it for hours/days it will not proceed, i can see a few products appearing but only a small number.
I figured the size was the issue, since it has 1200 lines.
So i already cut it down to 600, 400,200, 100 and 50 all of them have the same issue.
20 lines works, but that would take ages to process. Since this is also only one of the many CSV files i need to import.

Is there any way to figure out why it happens?