Script Error after Upgrade

One of my scripts is now not working after our upgrade.  I'm getting this error (which I have never got before):

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Account: 623926
Environment: Production
Date & Time: 3/23/2009 1:32 pm
Execution Time: 2.41s
Script Usage: 20
Script: Set Location on Bills and Credits
Type: Scheduled
Function: setLocationOnBillsandBillCredits
Error: SSS_INVALID_SRCH_OPERATOR
An nlobjSearchFilter contains an invalid operator, or is not in proper syntax: internalid.
Stack Trace: setLocationOnBillsandBillCredits(ServerSideScripts.js:60)
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The only problem is that internalid isn't called anywhere in my script!

Here's the script:

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var date = new Date();
date.setFullYear(2008,8,1);
var filters = new Array();
filters[0] = new nlobjSearchFilter( 'mainline', null, 'is', 'T');