Error updating on system that hasn't been used in a while

[Jargonaut]

Today I tried to get a copy of LOTRO to update on a machine I haven't used for several months. It downloads the Lotro launcher/executable, but then when it restarts and tries to update the data files I get this error:

PatchClientDLL::CheckDatFiles Failed. [Unable to decrypt and deserialize the data downloaded from the server.]

[Tralfazz]

Today I tried to get a copy of LOTRO to update on a machine I haven't used for several months. It downloads the Lotro launcher/executable, but then when it restarts and tries to update the data files I get this error:

PatchClientDLL::CheckDatFiles Failed. [Unable to decrypt and deserialize the data downloaded from the server.]

Try deleting that dll. First, be sure nothing related to the game is running – not the installer, not the LOTRO Launcher application, nothing. Then delete this dll:
*\StandingStoneGames\The Lord of the Rings Online\patchclient.dll

After that, run *\StandingStoneGames\The Lord of the Rings Online\LotroLauncher.exe as administrator. That will ensure that the launcher/installer/patcher has the permissions it needs to do its job. It will redownload anything it needs that it is missing so if your problem was with that dll deleting it will force the launcher to pull it down and install it again.

If that doesn't do the job, the next thing to try is a full deletion of your *\StandingStoneGames\The Lord of the Rings Online folder following by a reinstallation from scratch. This will not affect any of your saved preferences (keybinds, plugins, player music, etc.), those are stored in *\My Documents\The Lord of the Rings Online. It will be a bit time consuming, it is about a 34gb download; so try just deleting that dll and running the LOTRO Launcher application as administrator first.

[Jargonaut]

This is not a high priority so it took me a while to get around to trying again. But after copying a full working install from another machine, the error is exactly the same. The game files are fine, what else might be interfering in the game launch?

[auximenes]

Is that file flagged as read-only? Have you made sure your anti-virus is not misbehaving?

[cdq1958]

You can also try creating a new folder not in Program Files (x86), copying files there, running turbineregistergdf.exe and launching again, after pointing the launcher shortcut to the new location. This is partly why I did a custom installation outside of the default location. I find that I have fewer issues that way and do not have to run as administrator often. Windows is picky about permissions in its system folder locations.

[Jargonaut]

Just went through the rigmarole of a full re-install, though I did move the *.dat files to another folder to save the full download. NO DIFFERENCE. The exact same error occurs when trying to launch the game. An error I have never seen on any other machine. I give up. This machine is cursed and cannot run LOTRO. Time to do something else.