Are you hosting the site on iis? if so make sure the account your website runs under has access to local file system?
Straight from msdn .....
The Network Service account has Read and Execute permissions on the IIS server root folder by default. The IIS server root folder is named Wwwroot. This means that an ASP.NET application deployed inside the root folder already has Read and Execute permissions to its application folders. However, if your ASP.NET application needs to use files or folders in other locations, you must specifically enable access.
To provide access to an ASP.NET application running as Network Service, you must grant access to the Network Service account.
To grant read, write, and modify permissions to a specific file
- In Windows Explorer, locate and select the required file.
- Right-click the file, and then click Properties.
- In the Properties dialog box, click the Security tab.
- On the Security tab, examine the list of users. If the Network Service
- account is not listed, add it.
- In the Properties dialog box, click the Network Service user name, and in
the Permissions for NETWORK SERVICE
section, select the Read, Write, and
Modify permissions.
- Click Apply, and then click OK.
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