Animation presets are set to read only. You can't open up a preset with AE or any Adobe App. It's a script file and even if you opened it up with a script editor or text editor and tried to modify it, and then save it under the same name in the same folder you would have problems. Even if you opened up a preset in a script editor you could not edit it and save the preset and the preview unless you are a developer and have the developers package. Basically with animation presets there are no user serviceable parts inside. You can apply an animation preset, modify the settings, then save an the modified preset as a new one. The new preset will not have a preview. This is what an Animation Preset looks like in a script editor:
If you are trying to use Animation Presets by double clicking the name in folder then you are not using the right workflow. You either use the Animation menu and click Apply Animation Preset after you have a layer selected or you use the Effects and Presets Panel and find the preset you want to use and either double click it with your layer selected or drag it to the layer. You can also Browse Animation presets if you have Bridge installed. There were a bunch of bugs with Bridge in recent builds so you need to make sure that you have the latest versions of both running. In Bridge you should be able to see previews (eventually because some previews take a very long time to render) and pick them in Bridge and drag them to the layer you want to use or in some cases just double click. If you cannot drag or double click a preset in Bridge and have it apply to AE then you have some permissions problems or you have run into a bug.
If this does not point you in the right direction you need to provide us with th details of your workflow and how and when it fails. If there are error messages you should include them also. As always please include at least basic system info, your OS and version of AE down to the last decimal point, and any 3rd party effects or plug-ins you are using.