Thanks. I got Kontakt from Komplete, but those discs are long gone. Upgraded my Komplete to the latest one and of course its Kontakt 6+ only. I have an older 5.5.1 installer file, but can't seem to locate 5.8.1.
I believe if you installed 5.6.6 and updated it through Native Access, it would update to 5.8.1 (assuming you have a license for full Kontakt). Kontakt 6 is a separate product, so it wouldn't affect it. I have both 5 and 6 full and they co-exist fine and can be used at the same time.
Have you tried using that? I also got Kontakt via Komplete and the installer on my disc is probably older than 5.5.1, but here I am today with 5.8.1 installed (it's been years since I've reached for the disc; I've been performing regular updates through Service Center then Native Access). Give the 5.5.1 installer a try, then see if Service Center / Native Access detects an available update to 5.8.1.
Have another question @EvilDragon: Is there a reason why non-NKS libraries take ages longer to load? Like any library I load from the Library panel starts loading instantly, but everything else will hang for awhile before it begins loading in. I've tried resaving the respect NKI, but it doesn't seem to have much effect.
Usually there is a slight performance benefit when samples are packed in an NKX monolith, but not "ages longer to load" difference. If you're on Windows, add exceptions for Kontakt's file format extensions to your antivirus, so that they aren't scanned on file open (you don't want this to happen in a sampler).