I am having this error when installing a skin on a site.

I have the same site in multiple environments (copy of the directory and copy of database) and the skin installs just fine in other environments, but when I do it on the one, it fails with this message:

System.IO.IOException: The process cannot access the file '...\Portals\_default\Cache\39F21F870597871B46BA8F446DF665F9.resources' because it is being used by another process.at System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath)at System.IO.FileStream.Init(String path, FileMode mode, FileAccess access, Int32 rights, Boolean useRights, FileShare share, Int32 bufferSize, FileOptions options, SECURITY_ATTRIBUTES secAttrs, String msgPath, Boolean bFromProxy)at System.IO.FileStream..ctor(String path, FileMode mode, FileAccess access, FileShare share, Int32 bufferSize, FileOptions options)at System.IO.StreamWriter.CreateFile(String path, Boolean append)at System.IO.StreamWriter..ctor(String path, Boolean append, Encoding encoding, Int32 bufferSize)at System.IO.StreamWriter..ctor(String path, Boolean append)at System.IO.File.CreateText(String path)at DotNetNuke.Services.Cache.FileBasedCachingProvider.FBCachingProvider.CreateCacheFile(String FileName, String CacheKey)

It is failing when I do the install from host-> extensions and when I do the install by copying to the install/skins directory and visiting install.aspx?mode=installresources. What can I do?

There is only one virtual directory pointing at this dnn instance and it is in its own application pool (on windows server 2008 R2).

Recycling this pool does not get rid of the problem.

I think this is dnn 5.1, we are in the midst of upgrading dnn but that project has not made it to this site yet.