"The Documentation cache is still being constructed..."

This is probably old as h3ll and everyone except me has come across it. However I've been using Visual Studio .NET since there's been such a thing and I've never seen it before. I was looking to verify that ItemArray in a DataRow took object[] as the type of array.  So I get this goofy message.  I let it sit for about 10 seconds and nothing happens.  Then I click on the above property, click back down and it's still there.  Right then, the pizza guy showed up and I got my pizza and came back in.  Then it was back to normal. 

Has anyone else seen this?  At first I thought that whatever file VS.NET used for intellisense was generic for FCL Types and or stuf in the GAC.  But if that's the case, then it doesn't seem probable that it gets built over and over (I had Visual Studio .NET open already for a while).  Now with types I create, sure, this has got to be dynamic but I figured that VS might have some separation mechasinm. Anyways, I'm all in guessworld so I was wondering if anyone knew.  Also, does anyone know which file(s) specifically VS.NET uses for intellisense support and if so, how we can access it.  A co-worker of mine told me of one type he thought it might be (I can't remember the extension to save my life right now) but it was a C++ file and I couldn't make much from it (then again, I didn't try really hard either).  But know I'm curious and I'm trying to figure it out... if anyone has any clues to any of the above, please let me know...