GIMP Version: 2.6.11
Operating System: Windows
OS Version: Windows 7 SP1
GIMP Experience: Beginner Level

List any ERROR messages you received:
Failed to load data:

Fatal parse error in pattern file 'C:\Users\____\.gimp-2.6\patterns\texturemate-hexagon1-patterns.pat': Unknown pattern format version 65536.

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I keep getting ^ That error message when I try to load patterns. D8

You could be trying to load a PhotoShop pattern. I believe they also have .pat as their extension. PhotoShop patterns are not compatible with GIMP.

Yes even if you have a thumb.db file in your patterns folder Gimp will throw the same error.
Basically any file in your patterns folder that isn't a Gimp Pattern file will most likely throw an error.
To fix it remove the file.

That pattern file (texturemate-hexagon1-patterns.pat) is a Photoshop pattern file and contains multiple patterns in it. GIMP can't load it as a pattern and you need to remove that file from your pattern directory.

However, that pattern file should have come with the patterns as separate .png files and GIMP can load the .png files as patterns. (I just downloaded that file this weekend.)

Yes that is correct, any image file can be loaded in Gimp as a pattern usually.So if it came with an image example file use it/them.
You can also open or create any image file in gimp and save it as a pattern.
I suggest making it a tile-able image before saving it.
Edit/Copy - Edit/Paste as pattern - a new dialog will pop up asking you to name your pattern file.
Name it (same in both text areas), and refresh your patterns dialog.
I suggest making them all a max of 200x200 though or Gimp will take forever to load.

Specifically, any non-image files will cause the error. Gimp will happily take jpeg, png, bmp, gif etc. files it finds in the pattern directory and make them available as patterns.

-Rob A>