ASP.NET 2.0 Call Of MS SQL DTS Package Fails With Unknown User Name/Password

I am writing an ASP.NET intranet application on a Windows XP machine running IIS 5.1 which executes a MS SQL Server 2000 DTS package as part of the process. The application allows the user to select a UNC path of an input source (.txt) file to be procesed by the DTS pacakge and the UNC file path property is then set in the source object name of the DTS package tasks before executing the DTS package. Whenever I run the application using a file path that is on my development machine (the same machine that the web server is on) it works fine. When I select a source file path that is on a network share folder, the DTS package fails with the following error:

Event Type:      Error
Event Source:      DataTransformationServices
Event Category:      None
Event ID:      81
Date:            2/14/2007
Time:            12:58:06 PM
User:            N/A
Computer:      PHILSDELL2
Description:
The execution of the following DTS Package failed:

Error Source: Microsoft Data Transformation Services (DTS) Package
Error Description:Package failed because Step 'DTSStep_DTSDataPumpTask_2' failed.
Error code: 80040428
Error Help File:sqldts80.hlp
Error Help Context ID:700

Package Name: ATMRecon_ImportElanACHTxt
Package Description: (null)
Package ID: {3A8CC31D-A81F-40B7-BE57-AEB3AA238088}
Package Version: {B01420A7-ED22-49A7-B4C7-9FA1732394E3}
Package Execution Lineage: {2A9D45E8-35F8-4F0A-8339-7E5E29DA08B7}
Executed On: PHILSDELL2
Executed By: webaccess23
Execution Started: 2/14/2007 12:58:05 PM
Execution Completed: 2/14/2007 12:58:06 PM
Total Execution Time: 1.047 seconds

Package Steps execution information:

Step 'DTSStep_DTSExecuteSQLTask_1' succeeded
Step Execution Started: 2/14/2007 12:58:05 PM
Step Execution Completed: 2/14/2007 12:58:05 PM
Total Step Execution Time: 0.047 seconds
Progress count in Step: 0

Step 'DTSStep_DTSExecuteSQLTask_2' succeeded
Step Execution Started: 2/14/2007 12:58:05 PM
Step Execution Completed: 2/14/2007 12:58:05 PM
Total Step Execution Time: 0.047 seconds
Progress count in Step: 0

Step 'DTSStep_DTSDataPumpTask_1' failed

Step Error Source: Microsoft Data Transformation Services Flat File Rowset Provider
Step Error Description:Error opening datafile: Logon failure: unknown user name or bad password.

Step Error code: 80004005
Step Error Help File:DTSFFile.hlp
Step Error Help Context ID:0

Step Execution Started: 2/14/2007 12:58:05 PM
Step Execution Completed: 2/14/2007 12:58:06 PM
Total Step Execution Time: 1 seconds
Progress count in Step: 0

Step 'DTSStep_DTSDataPumpTask_2' failed

Step Error Source: Microsoft Data Transformation Services Flat File Rowset Provider
Step Error Description:Error opening datafile: Logon failure: unknown user name or bad password.

Step Error code: 80004005
Step Error Help File:DTSFFile.hlp
Step Error Help Context ID:0

Step Execution Started: 2/14/2007 12:58:05 PM
Step Execution Completed: 2/14/2007 12:58:05 PM
Total Step Execution Time: 0.031 seconds
Progress count in Step: 0

When I check the Security Event Log on the server on which the network share is located, I find the following set of messages repeated multiple times:

Event Type:      Failure Audit
Event Source:      Security
Event Category:      Account Logon
Event ID:      680
Date:            2/14/2007
Time:            1:02:48 PM
User:            NT AUTHORITYSYSTEM
Computer:      FS1A
Description:
Logon attempt by:      MICROSOFT_AUTHENTICATION_PACKAGE_V1_0
 Logon account:      ASPNET
 Source Workstation:      PHILSDELL2
 Error Code:      0xC000006A

Event Type:      Failure Audit
Event Source:      Security
Event Category:      Logon/Logoff
Event ID:      529
Date:            2/14/2007
Time:            1:02:48 PM
User:            NT AUTHORITYSYSTEM
Computer:      FS1A
Description:
Logon Failure:
       Reason:            Unknown user name or bad password
       User Name:      ASPNET
       Domain:            PHILSDELL2
       Logon Type:      3
       Logon Process:      NtLmSsp
       Authentication Package:      NTLM
       Workstation Name:      PHILSDELL2
       Caller User Name:      -
       Caller Domain:      -
       Caller Logon ID:      -
       Caller Process ID:      -
       Transited Services:      -
       Source Network Address:      10.120.4.61
       Source Port:      0

The problem appears to be that the DTS package is trying to access the input source file using the local ASPNET Id from PHILSDELL2 which does not have authority to the network share.  The ASP.NET application is using impersonation, set up through the web.config file:

  <identity
       impersonate="True"
       userName="registry:HKLMSOFTWARESkylightATMReconidentityASPNET_SETREG,userName"
       password="registry:HKLMSOFTWARESkylightATMReconidentityASPNET_SETREG,password"
    />

The application can sucessfully access the network share under the impersonated id (the application first verifies the existience of the source files before executing the DTS package). I have wracked my brain trying to determine where the ASPNET security context is coming from to no avail.  Can someone shed some light on what security credentials the DTS package is using to access the source files and how to change them?