New Post: Paypal IPN don't work! (DNN7.2.1 NDStore 2.3.8)

Hi Robax!
Thanks for your response!
Instead to change friendlyUrl configuration I've try to change the notify IPN URL with this: http://mywebsite/Checkout/stg/4
Now Paypal IPN is able to achieve NBStore IPN page but looking at Event Viewer I can see an exception:

AssemblyVersion:7.2.1
PortalID:1
PortalName:My Web Site
UserID:-1
UserName:
ActiveTabID:121
ActiveTabName:Checkout
RawURL:/Checkout/stg/4
AbsoluteURL:/Default.aspx
AbsoluteURLReferrer:
UserAgent:PayPal IPN ( https://www.paypal.com/ipn )
DefaultDataProvider:DotNetNuke.Data.SqlDataProvider, DotNetNuke
ExceptionGUID:4b252b20-256f-4356-a208-cac286bb7e24
InnerException:Arithmetic operation resulted in an overflow.
FileName:
FileLineNumber:0
FileColumnNumber:0
Method:Microsoft.VisualBasic.CompilerServices.Conversions.ToInteger
StackTrace:
Message:
System.OverflowException: Arithmetic operation resulted in an overflow.
   at Microsoft.VisualBasic.CompilerServices.Conversions.ToInteger(String Value)
   at NEvoWeb.Modules.NB_Store.Gateway.PayPalIPNParameters..ctor(NameValueCollection requestForm)
   at NEvoWeb.Modules.NB_Store.Gateway.GatewayPayPal.AutoResponse(Int32 PortalID, HttpRequest Request)
Source:
Nome Server:WEB001

If you need I can send you privately the IPN Message posted by Paypal