About 2 days ago our vbulletin site, seems to have broken. No changes had been made for about 6 months previously. We rebooted the machine, same issue. We looked into other php/mysql combos for other sites I host. No issues with those. If you wait long enough the site will display and function correctly.
I did a repair/optimize of the tables. Same behavior. I also updated to 3.8.6 and same issue. We are running vbseo, I disabled that as well and same issue. We even used the default theme for a test user and we still see it slow.
I am kinda out of ideas. I don't see anything wrong or taking a while. Any pointers on where to look next?