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Windows 2003/2008 servers (IIS6.0/IIS7.0) configured to prevent uploading files over 200kb by default. Contact your host and ask them to increase the default upload limit.
Here is a set of instructions:
IIS 6.0 on Windows 2003 has a file named metabase.xml which resides in the folder:
C:\Windows\system32\inetsrv . By default, this file has this entry:
AspMaxRequestEntityAllowed = "204800"
This limits upload size to 204,800 bytes. You can change that to a large value (such as 20480000 for 20 MB for instance) to allow your Windows 2003 server to accept large uploads.
You would need to stop IIS before you can edit this file.
Note: In IIS7.0 this configuration is available in generic IIS manager.