It sounds like an obscure bug in Windows Scheduled Tasks. Some things to try:
1) Configure both tasks to run under the same user account.
2) Use AT instead of Scheduled Tasks (discussed in the 'scheduled builds' help topic)
3) Use an alternate task scheduling application (
http://www.google.com/search?hl=en&i...duler+software).
4) Upgrade to the latest server software (Windows Server 2003) with all patches and hotfixes.