Since we're passing an HttpInputStream to the DLStoreUtil, the stream will be exhausted by the antivirus check before it can be persisted into to the store.
Steps to reproduce:
1) Enable antivirus check:
2) Download an App via the Market Place portlet
3) Try to install it
Since the file in the DL store is empty (0 byte in size), this operation will fail (ZipException) and the UI will display the Download button again.