Unreasonably high CPU usage

Hi! I'd like to report a problem with GP-150 (the newest build today [2013.08.05]).
When I start the server up, it uses 5-10% of my CPU, which is quite low. But when at least one players joins, it goes up to 50-60%. If I restart it without GP, the problem is solved.
I'm not a developer at all, but using spigot's timings, I have been able to find out, that the blockFromTo event is being called 1,094.80k times in a few minutes with one player on, and that is what could cause the problem, but that's just my guess.

Specs: Win7 Ultimate, 32bit with 2 gigs of RAM, 1 allocated to the server. AMD Athlon Dual core on 2.2GHz. (this problem has been tested on Intel i7 with 8gigs of ram, 2 allocated to the server, and still exists.)
Java's version is 1.7.0_25

I hope it can be fixed.
- DecentM