check where your "additional rendering appearance paths" are pointing, under file>options>Rendering If these paths are to a network or if material maps its looking for in these locations are missing it will cause it longer to open the materials dialog box.

Thanks Scott, but that wasn't it. I checked and that list is empty.

I am very confused about this, something is somehow corrupted or its looking for something, but I don't know what?

Rephrasing the question. Does anyone know what files Revit access in relation to the material library? Revit.ini?

MaterialConfig.xml in Roaming App Data, and whatever ADSKLIB's are specified in it, and all of the Additional Render Appearance Paths, which are listed in the INI.

By MaterialConfig.xml, do you mean MaterialUIConfig.xml? If so, I've looked in that one and it only seems to address the sizes of various dialogue requesters. I compared this one and Revit.ini to another (working) system and they are almost identical, so it does not seem as any of these affects the problem.

Is there a way to get Revit into a vanilla, freshly installed state? I'm thinking that I've upgraded Revit all the way from 2016 on this system and I'm not sure if Revit migrates anything when it finds old installations. Is Revit depending on any critical registry settings?

I guess its getting technical, but if anyone has the experience to figure it out its this crowd.

I first noticed this in 2015 or so after loading the lysaght material library. Subsequent loads of the library in later versions have not as much time loading, but do take a few more seconds. I have thought about the render appearance library links in options as well, but from what i can understand am i right in saying i would have to link EACH folder of their products containing images and not just the MAIN parent folder with the subfolders in it?

Yes, i meant MaterialUIConfig.xml. If you have ADSKLIB's specified to be loaded, that is where they are set.

The different years of Revit installations are in no way related to one another, and nothing gets migrated forward. Revit DOES have TONS of registry settings, all over the place, though.

One other thing to note is that MaterialUIConfig.xml also controls the UI state of the Materials Dialogue. For instance, i have my Materials list set to Text List, instead of Preview images. Reason being, it takes time to render those preview images. Mine opens up blazing fast.

I was in an office for a client this week, and theirs drags ass too. Whats funny about that, is there materials were all loading from a local path, and mine all load from the network, and are faster.

One thing to check, is if there are materials in your project that are specifying images that are MISSING from your render appearance paths. It wouldnt make sense that that was the case for one of your machines and not another, but it IS possible.

Since we all use the same server, I guess that would mean that it is something another machine has locally but not mine. Wouldn't Revit complain if it couldn't find something? Does it have a journal or log file with error messages somewhere?

I've tried reinstalling Revit but that made no difference, however I would like to reinstall the material library part alone. I also have 3ds Max installed and have a feeling not all got uninstalled properly since it may be seen as shared. There is an uninstall tool, but using Setup only allows me to install the major apps (we have building design suite).

I don't quite follow, where do you link these folders?