Same problem here: execute "!start regedit" (just a sample) works fine with 7.3.441 (last version I updated to); it's no longer working in 7.3.446:
441: !start regedit.exe => regedit starts 446: !start regedit.exe => E371: Command not found -- You received this message from the "vim_use" maillist. Do not top-post! Type your reply below the text you are replying to. For more information, visit http://www.vim.org/maillist.php
