Wrong Tax amount on Invoice PS1.3.1

[DKM84]

Hi,

I am using PS 1.3.1 and I am having some trouble with the numbers on the invoice
There is a difference between the totalswithouttax and the productwithouttax

sample:
http://imageshack.us/f/217/factuurfout.jpg/

I tried to fix it by checking with newer versions of the PDF.php but I can't seem to get it right. (due to lack of programming skills)

I found out that there were soms peeps with te same problem but no solution was provided.
Is there a fix or workaround for this?

Thanks in advanced