Error seen when calling 7z rapidly from a script.

[Bob]

I have found that if I have a .BAT file that calls 7z rapidly multiple times it throws an error like:
7-Zip cannot move the file
Archive.tar.tmp

Access is denied
using:
7za.exe a "%ARCPATH%.tar" <file path="">
7za.exe a "%ARCPATH%.tar" <file path="">
7za.exe a "%ARCPATH%.tar" <file path="">
7za.exe a "%ARCPATH%.tar" <file path="">

Putting a 1 second delay after each call seems to fix the problem:
7za.exe a "%ARCPATH%.tar" <file path=""> && sleep 1
7za.exe a "%ARCPATH%.tar" <file path=""> && sleep 1
7za.exe a "%ARCPATH%.tar" <file path=""> && sleep 1
7za.exe a "%ARCPATH%.tar" <file path=""> && sleep 1

Win XP+SP3+all updates
7z is 9.22