The correct permisions required to access the SQL Snapshot folder are as follows
SQL Server Agent (AUTODESKVAULT).
By default this service uses the "Network Service" windows account. If configured differently or a mix of Domain\workgroup environments are being used, the SQL Server Agent account must have (read for Subscribers and read-write for publisher)
SQL Server (AUTODESKVAULT)
By Default this is the "Network Service" account. if different than the default, it needs read-write permsissions.
Vault Impersonating Account
By Default this is the "AutodeskVault" user account. In Vault Collaboration\Professional 2011, this account must have read-write.