Error message: The process cannot access the file 'C:\inetpub\allforoffice\minified\core-css-files.min.css' because it is being used by another process.

Url: http://allforoffice.gr/skin.aspx?lang=en&action=newarrivals&categories=0162D43A‡43C2E580‡FC5A23B0‡F8077BC9‡F73347A7‡B472BA8D‡61F84793‡2A7804DB‡51466317‡84C5F8DC&splitter_products_offset=0

Message: The process cannot access the file 'C:\inetpub\allforoffice\minified\core-css-files.min.css' 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, Boolean useLongPath, Boolean checkHost)
   at System.IO.FileStream..ctor(String path, FileMode mode, FileAccess access, FileShare share)
   at System.IO.File.Open(String path, FileMode mode)
   at Bone.Minifier.MinifyCssFiles(String[] files, String name) in C:\Bone\Bone\src\Classes\Minifier.cs:line 252
   at Bone.Minifier.MinifySection(String html, String name) in C:\Bone\Bone\src\Classes\Minifier.cs:line 365
   at Bone.Base.get_HeadMinified() in C:\Bone\Bone\src\Classes\Base.cs:line 523
   at ASP.skin_aspx.__Render__control1(HtmlTextWriter __w, Control parameterContainer) in c:\inetpub\allforoffice\skin.aspx:line 25
   at System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children)
   at System.Web.UI.Page.Render(HtmlTextWriter writer)
   at Bone.Asp.RenderSkin(TextWriter w) in C:\Bone\Bone\src\Classes\Asp.cs:line 71
   at Bone.ModalAction.RenderPage(TextWriter w) in C:\Bone\Bone\src\Actions\Modal.cs:line 81
   at Bone.Asp.Render(HtmlTextWriter w) in C:\Bone\Bone\src\Classes\Asp.cs:line 82
   at System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter)
   at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)