Is this a PKWARE ZIP 2.04g industry-standard archive format? Can you extract it with Windows Explorer (without an external tool), just the built-in ZIP functionality in Windows (which also supports the industry-standard ZIP format).

BTW, we are using the LSZip library to process ZIP files. This component is used on 20+ million machines worldwide since 1997. LSZip is certified (by Phil Katz of PKWARE, the developers of PKZIP) to be 100% PKWARE 2.04g archive format compatible.

It's very well possible that an external process (anti-spyware; anti-virus) monitors the ZIP file during the unzip process and this causes it. It suddenly detects an end-of-stream (because the external process locks it) and switches into multi-archive mode. There is a fundamental difference between unpacking a file using WinZip or Winrar and unzipping a file as part of a setup. Most setup processes are permanently real-time monitored at runtime. BTW, the ZIP component is feature and code complete (for more than 5 years) and there will not be any update in the future. It is very unlikely that there is a bug in the ZIP component.

Friedrich