Heavy GUI Lag!

[DuBrony]

I recently got Amnesia: The Dark Descent. After turning down some graphics settings, SSAO, resolution, etc., I got NO problems when playing. However, when I tried to bring up the inventory, the framerate drops so badly, it'll take 3 minutes until the inventory goes away (after holding the TAB key the whole time >.<). The same goes for the 'esc menu', mementos, journal, and various papers laying around the castle. After going through a few pages, I gave up. It really makes the game unplayable, especially when my lantern ran out of oil. I can't even put oil in it without waiting several minutes for a single frame to pass!

I updated my graphics card when I got Borderlands on my computer, and it works great. The same goes for Left 4 Dead 2, Portal 2, Mirror's Edge, and a few other demanding games that I have. Here are my specs:

Spoiler below!

Windows XP Professional (5.1, Build 2600)
Intel® Core™ Duo CPU (Laptop, btw) T2250 @ 1.73GHz (but rated at 2.38GHz)
2.1 GB RAM

ATI Mobility Radeon X1300 (0x7149)
128 MB memory
1280x800 resolution (but I run games at smaller, like 800x600, for a serious FPS boost, try it sometime)
Hardware T&L: Yes
Pixel Shader: 3.0
Vertex Shader: 3.0

some information was gathered in the DirectX Diagnostics Tool (dxdiag), and some at 'Can You RUN It?'
( http://www.systemrequirementslab.com/cyri )

Any/all forms of fixing this issue is grately appreciated.