Time to time board very slow

[mp3president]

Hi there,

For the last couple of months my forum is multiple times a day very slow for some reason!
So slow, that i have to reboot my server almost every day.
On the server there is another forum running, also VB4 and that one has no problems.

Things i have tried already:

1. Did not installed any new mods in the last months.
   
2. Excluded every mod i have by my idea. Shut them off 1 by 1 to see if a mod has issues, but no luck here.
   
3. Excluded a couple at the same time, to see if there for some reason suddenly is a conflict, also no luck.
   
4. Clear cache in ACP does not do the trick.
   
5. Looked at my forum for any slow pictures from outside image hostings, but also not the problem.

Strange thing is, i do not always have to restart my server. Many times it goes away on its own, stays fast a couple of hours, and then out of no where it is slow again but the other forum is not.

So it is not a server problem, it is in my board somewhere.

Could this maybe have to do with upgrade from 4.2.4 to 4.2.5?

Is there anyone who has some tips where to look? Is there some sort of diagnostic mod that runs through all your forum and mods looking for errors?

In maintnance under "repair and optimise tables" when i want to do that, i get the 503 server error. So this does not work.

I hope there is someone that can help me!

I am also thinking of build a new board, as my old board is, and then import all my topics and users into that one and see if the problem stops.
How do you think about that? is this an option?

Regards
Mp3president