Upgrading DLLs to VFP9 SP2 may help you in troubleshoting. See http://www.berezniker.com/content/pages/visual-foxpro/aerror-function-returns-extended-information-errors-1104-and-1105-visual

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>We are maintaining an Web application developed in ASP and backend being Visual FoxPro 8. We create/build Web DLLs in Visual FoxPro 9 SP1 and they are used to act as a bridge to the web application and the backend tables.The Visual FoxPro DLLs are configured as COM+ components.
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>We have error handler in our web application. Consistently, we receive error mails from, "Error 1104: Error reading file". The thing is it get solved immediately without any manual intervention.
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>We could not able to figure out the cause of this error. Please guide us.
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>Earlier the web dlls are built in VFP6 SP5. We received this error 1104 mails consistently. We had migrated web dlls from VFP6 SP5 to VFP9 SP1. Even then we had received this errors consistently.
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>Please let me know that simply migrating from VFP6 SP5 to VFP9 SP1, the application will be running with VFP6 SP5 behaviour.
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>Is there anything we have to perform for migrating VFP6 SP5 to VFP9 SP1 like
>1) Is there any specific compilation steps to be done?
>2) Is there any environmental settings changes to be done ?
>3) Is there any mandatory steps to be done?
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>Thanks,
>Sukumaran