I tried to ask a question in this site. While doing so, I get this warning message that says "You can only post once every 40 minutes.". However I have not asked any questions in the past five months. I asked a question on another network and that too was 2 days ago.
Most likely someone on your network asked a question somewhere on the network and doesn't have a lot of reputation so far. See for example this answer to Potential privacy breach due to question rate limit from IP addresses:
You can post only in 40 minutes in the network sites in which you have a low rep.
If from anyone in your office with low rep, asked a question in any network site, that should be the reason.
It is a network wide limit for low rep users.