Okay, I have been encountering this bug a lot lately, but wasn't quite sure why it was happening, or what it even was. I wasn't sure if it was my graphics card, my CPU, Graal, my computer...
Anyways, I narrowed it down and found out the problem.
Whenever Graal is currently the window in focus(AKA an active window), but another process of sorts is taking priority, Graal cranks up and starts taking 100% CPU. An easy way to replicate it:
Open Graal, open the Task Manager to watch your CPU. Keep Graal as the active window though. Then open the start menu. Graal's CPU shoots up to 100% CPU fast, and it slows down my computer horribly.

I'm not entirely sure if this applies to everyone though, or if it's just my computer/set-up. Either way, I decided to test it with the Graal editor. I opened it up and played in a level with lots of NPC's and such running and did the above, and it did not do the same thing. It ran perfectly fine. I also tested it with other intensive programs like Photoshop CS3 and such. No problems with them either.
It's not INSANELY problematic, as Graal runs fine, and most other programs run fine since they steal focus... but it's annoying nonetheless. Watching menus stutter into view because Graal is hogging CPU is ugly to watch.
PHP Code:
Operating System: Windows XP Professional (5.1, Build 2600) Service Pack 2
Processor: AMD Athlon(tm) II X2 250 Processor, MMX, 3DNow (2 CPUs), ~3.0GHz
Memory: 2048MB RAM
Page File: 369MB used, 3570MB available
DirectX Version: DirectX 9.0c (4.09.0000.0904)
Card name: ATI Radeon HD 4600 Series
Display Memory: 512.0 MB
Driver Name: ati2dvag.dll
Driver Version: 6.14.0010.7060 (English)
Driver is up-to-date as far as I'm aware since I've recently downloaded and installed it. Graal version is
v5.
edit: Also noticed if I have Graal running(and focused, as in playing it) with Photoshop CS3 in the background, Graal is taking 100% CPU... making it impossible to play. Just because Photoshop is running behind it.

This is when it becomes really annoying because it makes it hard to play Graal and work in Photoshop at the same time...