Severe "lag" in 0.2.5

[Drawde]

I've noticed with 0.2.5 and 0.2.4b6 (but not b5 or earlier versions) that there is usually a delay between clicking/pressing a key and the action being carried out when doing anything "server-side" - considering a NPC, purchasing an item, casting a spell etc. The delay is anything from 5 to 30 seconds.
Client-side actions like jumping, moving items about in your inventory, etc. do not cause a delay.
This is on an entirely local server, using minlogin.
It's a very annoying problem, and makes melee combat nearly impossible, and everything else very slow and tedious. Has anyone else encountered this problem, and is there any way of dealing with it? I haven't had this problem at all until 0.2.4b6.