Performance problem using NAV Three Tier

Hello,

I have a performance problem using NAV Three Tier in a Job.

First, I´ll try to explain how is the architecture. We are using NAV three tier for communicate a web shop with a sync Bridge developed on .NET, who calls NAV using web service.

Currently we are using two types of webservice, for create a correct structure for us, who is a Contact, Customer and Vendor and an Sales Order for the users who are logged on our web (we send a gift to logged users, and customer wants these data reflect in NAV).
Services published are:

1) The page webservice, publish contact card, and NET use it for made an insert.
2) The codeunit webservice, has 3 methods published, one to inser customer, one to insert vendor, (relating both to the contact), and one who makes the sales order with one line with the gift (not posted, only insert).

These Web services are called in order. After The reason for this post, is the next:

- When we make consecutive calls to generate 5000 users, calling all the services, all goes ok.

- When we make consecutive calls to generate 27000 users, calling all the services, problems occur, like cursor error ID:24000, deadloks, etc...also the SQL Server memory occupied by progressively lower until the server crashes.

Currently, we are using SQL Server 2008 with 4Gb RAM. How can we solve this problem? too many records?

Thanks,