I have been trying to figure out a pattern to this issue but to not avail.
I've disable my Norton anti-virus which help for about 15 minutes. Then the lags came back.
My project file is fine.
The only odd thing I can point out is watching my task Manager under performance tab my CPU's are acting funny. I did have a couple of early morning meassages that the CPU what running hard.
When Inventor lags, only 1 (sometimes 2) of my 12 CPU's is maxed out while the others are sitting idle. I have no other applications or services adding to this.
Are the files stored on the local machine or on a server. If it's on the server, try copying files to the local machine and test run it locally.
Try a system re-boot, look for other applications hogging memory. On the reboot it wouldn't hurt to open the case and see if your machine needs to be "blown-out" If a CPU is overheating it will throttle-back to reduce heat. Also check that all the memory boards are properly seated along with the graphics card and it's connections.
You should also be able to put exlusions in your Anti-Virus to ignore Inventor files: *.ipt, *.iam, *.idw and *.ipn.
Have you tried anything like Process Explorer? It might give some insight as to what is taking all the cycles.
Tried everything suggested thus far, nothing works. I'm even on a fresh install, it keeps locking up out of the blue. One day it'll be fine all day, and the next I have to kill the process every 5 minutes because it's preventing me from doing any work.
This is getting quite aggravating.