After a long and heated conversion with my bank (the one I got my prepaid card) I learned a few things.....
1. There is a new ''Service fee'' introduced in June for every purchase made in dollars (because my account is in euros) There is a 2% charge up to a maximum of 5€.
2. My home address has changed in the system (it's used to verify me for secutiry reasons) and I had to give my old address to get verified (I've moved out of there 3.5 years ago).
3. Transactions can dissappear from my purchase history. And it's not just my idea, I spoke to a different person last week and the purchases I made were there and he confirmed them. Today they're gone. My card balance has not changed though....
4. Questions at the ATM about my card balance can dissappear too from my card history.
5. And lastly (which is the reason I phoned them 3 times up to now) my cards remaining balance does not equal my purchases. On two occations I noticed a smaller charge by 11.01€ and a bigger charge by 15.27€. (I use an ATM to regularly check my cards balance)

So I come here and ask your opinion and experience.
Has anyone encountered one or more of these "malfunctions" in their own bank? (Especially in the euro zone)
Should I ditch them and go to another bank?

No. We have several major banks here (and aside from the odd brainfart affecting a given set of customers), none of the banks i had been with ever had such a weird set of problems for a customer. Time to try another bank methinks :)

Which bank if I may ask?

I haven't seen this problem, but i'm in the US.

I also deposit $100 at a time into paypal and transfer from the floating balance (which seller fees is usually like 40 cents per transaction...)

They have offered me the option to go to a local bank and file a "controvert transaction application" but I doubt this will fix anything.... Yeah, I trust paypal, but it's convenient only when buying in euros. When buying in dollars I noticed an extra charge about 4% more. (that goes to paypal, not to the bank)

Ouch... Where's Jesus with his whip when you need him...

If worse comes to worse, i'd be willing to purchase US visa gift cards and trade them straight up... As i understand it Credit Cards take about 3% of the total purchase value of an item; When compared to Paypal which does 35 cents + 2% up to $200; For small purchases (and weekend deals) it would be much better to take this route, and GoG could feel less loss from them. (And if you don't like filling that information out at the checkout, i can make a AHK script to do the job easily...)

Of course if they add in a wallet balance feature (add money to GoG directly up front beforehand) to then that would be even better... Plus you wouldn't have to sign in to PayPal to confirm the transaction, it would be instant... Good for those odd flash deals or when there's like 10 of something left on their insomnia deals.

edit: There's a note elsewhere regarding using Visa as gift cards and it not working, so i'm not sure how well i could offer this... :(