There are 2 reasons this can happen.
There is currently an issue if you are running Lackey from a USB drive, and that drive is not formatted the same as your main drive. To fix this, either don't run Lackey from a USB drive, or reformat the USB drive to be the same format as your main drive.
The second and more likely issue is you are using a different plugin as your opponent. This can be caused by one player not updating, or one player adding or removing a card data file to their sets/ folder. You SHOULD be given a warning when you join a game if this is your issue. The warning should read "WARNING: PlayerA's plugin is not the same version as PlayerB's. This could cause errors, like seeing the wrong cards." You also should see their game on the server as red to you, further indicating that you should NOT join this person's game. One way to check if your version is different than his is to go in the deck editor, and read the number of Total cards in the deck editor library. (It should say "Total:#") If your total does not match, then one of you is using the wrong version of the plugin.
To fix the issue, you should run autoupdate again, and relaunch. If that still doesn't fix the issue, delete your entire plugin and reinstall it, and relaunch. If that still doesn't work, and both players have performed these steps, then please report it here.
In your report include your name, and the other player's name, as well as if you have this issue with other people, and if they have this issue with other people. Also report your plugin name, and the version (medium or high) and their version (medium or high).
EDIT: Another reason you will see wrong cards is if you installed extra txt files to your sets folder (or altered some of those text files). To fix this, delete all txt files in your sets/ folder, run autoupdate, and then relaunch.