Slitherine

Hi I purchased FOG yesterday and tried to play an on-line multiplayer game. I was told I had an old version and had to download patch. The patch fails to install. Last few lines of Updater follow below, 2013-03-12 08:43:49 Read 19666884 OK. (E=19666884, A=19666884)
2013-03-12 08:43:50 The downloaded file's signature is correct.
2013-03-12 08:43:50 Error while extracting file:Could not read central file header.
2013-03-12 08:43:50 Could not extract the file.
Please help.

Welcome.
Try instead, downloading the update manually. Download the patch (1.8.1) from one of these mirrors:

http://www.matrixgames.com/products/378/downloads/

Unzip the downloaded file. Run the extracted file to install the update.

Thanks that worked as far as being able to run the patch. However the FOG program now gives a runtime error which follows below.
..\..\..\..\Common\plugin.cpp:7458
Failure Condition: pluginEntryTable.GetEntry( entrypointName,out )
can't find plugin method DecodeBase64(data As String, encoding as TextEncoding = nl) As String

That usually indicates a corrupted installation.
You should uninstall the game, locate the folder where the game was installed and delete any leftover files. After that you can install the game again and run it. If everything is all right, then you can proceed with the installation of the update. If you still have the patch, then use it and update the game manually, otherwise download it again from the same mirrors.