create subdirectory failed on Local network server, please help

 vs2008, use vb.net to implement create a subdirectory on server. I have set directory full control like "\\10.183.1.90\New Folder"
Below is the vb.net code use for "create subdirectory" and I invoke this function "createDirectory("\\10.183.1.90\New Folder\new1\new3\")", found that I use vs2008 to debug the folder can be created successful. but if i config to IIS and visit, system will generate error as "System.Runtime.InteropServices.COMException : Logon failure: unknown user name or bad password".
please help me.
Protected Function createDirectory(ByVal directoryAddress As String) As String
    ...