Problem redeeming GV-Balance

Hi folks,

I am sorry but I do have a little problem. My GV-System is working in regards of buying a gift-voucher and releasing it from admin. It appears as a balance on the customer site, but when I enter an amount which is equal or less than the voucher balance it goes to confim order page without dedurcting the amount from the total order sum. There is no error message or something. For testing I entered an amount higher than the available balance. As aspected I got an error message for spending to much. Is there some special setting which I do miss out? I tried everything like small order amounts and big order amount. I tried full EUR amount as well, but always I got the same result.

I am using 1.3.7 and I know everything worked fine a couple of upgrades before. But because I do not have a lot of GV, I missed to check where the trouble started down the line...

Any help? Thnaks in advance...

Dieter