Oracle ODBC / ColdFusion Question

We recently deployed two servers for an application, a web server (ColdFusion Server 4.5.1 Enterprise Edition) and an Oracle database server (8.1.5). We are using ODBC to connect from the web server to the database, and this works fine. Yes, we will be switching to native Oracle drivers as soon as we re-tool the application a little bit.
The web server is hung outside the firewall and a hole has been punched through the firewall to connect to the database server. Both servers are in physically different buildings.

We have a problem... if the web application is idle for a while--the exact measured time is not known--the web server seems to lose the connection with the Oracle database, and at the login screen for our app--the app queries an application security table-- we get a "ODBC Error Code = S1000 (General error)".

However, when I go to the database server and ping the web server, all queries from the web pages work fine after that. Is there some sort of pinging process that occurs between Oracle and ColdFusion? I am familiar with Oracle in a client/server setting and sometimes we had to set the sqlnet.expire_time parameter, but this seems a little different. I would like to keep expire_time at 5-10 minutes. I am also used to the native drivers in Oracle, and am not entirely familiar with ODBC. I did set the connection duration for the ODBC datasource in ColdFusion to five minutes, and my understanding is that is per connection. Either the connection is being severed, or something is clogging up ColdFusion, which I think is a great product.

Any suggestions?

TIA,
Joe

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e-nough already.