I'm experiencing the same error too. I was unable to make payments through all channels (time card, crysta, credit/debit card, and paypal). I used to have problems with the debit card payment until I stopped playing before HW. I started playing again once I was able to purchase crysta last January. It was fine up until a couple of days ago when I tried buying crysta and I got error i2501. I tried all methods and even bought a 60 day time card and i still got the same error. Sad part is there are about two internet posts about it with no solutions.

I reported it via chat last friday, no update yet. Calling the support number is too expensive for me and it's also the weekend so... i wanted to play soooo bad...