Random "no Payment Method Is Available For Use At This Time" Error

[woodland]

• Presta 1.6.1.1
• PayPal USA, Canada 1.3.9 (PayPal Payments Advanced)
• Advanced stock managment enabled with two warehouses
• Multistore - each store has it's own warehouse
• About 3k products (some with 0% tax and some with NY tax rate about 8%)
• Guest checkout disabled
• One page checkout enabled
• Templatemonster Theme
• Two carriers available for Customers group
• Free shipping from $99.01

Hello,

 

I'm looking for any help with "No payment method is available for use at this time" error that is randomly showing in cart. Some clients can put few products in cart and never notice any problems and other clients when different products are added see this error. Then when I make the same problematic cart and remove one or two products - the error disappears. But then when I use those products in different cart I don't see the error.

 

Only thing that always clears this error is adding promotional code for any amount for example 1 cent. When I put such promo code in the cart with this error, the error will be gone.

 

I'm not sure but sometimes it looks like this error is showing when cart contains more than 8 different products. But not always.

 

I've re-did advanced stock management settings in all products. Everything looks ok, but maybe I've missed something.

 

I'm looking for community or paid support.