So far as I can tell (I purchased the game yesterday and have been doing some research online about this issue), the slowdown that occurs when text is displayed on screen seems to affect newer cards (DX10 perhaps?) on Windows Vista/7. Lowering the resolution down to below 1024x768 has somewhat relieved the problem, but whenever there is lots of text on screen (i.e. reading the journal), there's still slowdown.

I've pretty much run the gamut of "fixes", from setting CPU affinity, to enabling and disabling most of the options in the Nvidia control panel, to messing around in the Arx config file (notably the forcegdi setting), to replacing the game's fonts with my own system fonts, all to no avail. I've even tried downgrading to patch 1.18, which retained the font problem, but also introduced the old problems as well (lights being visible through walls).

I know there are workarounds suggested on this forum which go as far as removing battle text from the game to limit the slowdown to areas of the game which aren't action-oriented, but I would really like to be able to keep that stuff intact and try to find a solution that allows me (and other Arx users running modern OSes) to play the game without resorting to blurry resolutions or other workaround which degrade the experience of this awesome game.

My laptop specs are: Core 2 Duo, 8600M GT, 4GB RAM. My monitors native resolution is 1680.x1050. The game runs perfectly when there is no text on screen, but becomes extremely laborious to play, especially when precise clicking is involved in the inventory or journal, when text pops up.

Sorry for the long post, but there doesn't seem to be that much attention paid to this issue, and I'm sure I'm not the only one still experiencing it now that so many are running Windows 7 and DX10 cards. Any insight into the problem would be appreciated. Thanks.

v1.19 was supposed to make some changes to font handling. I haven't seen this slowdown myself since I'm already running at 1024x768.

In the patch notes for 1.19 it mentions how anti-aliasing is used on fonts, so I tried disabling AA by forcing it off in the Nvidia control panel, but that didn't help. I'm not too sure it's that, though, because even under 1.18, I was experiencing the font lag along with the see through lights.

That's the same issue that bugs me on GTX 280. I believe that's not antialising but rather font scaling (doesn't really make any difference)
And the most annoying is that patch 1.21 that supposedly fixes issues for Nvidia users doesn't affect this issue at all!

I believe we may see a fix later, now that the source code got released.

You might try this:

http://www.gog.com/en/forum/arx_fatalis/unofficial_patch_with_performance_and_bug_fixes

Unofficial patch, I believe put together by 'Nuky' (on the forums). It apparently included general performance improvements, but it almost entirely fixed this problem for me. This is on a GTX 465, other people have said it hasn't worked for them, but you should definately give it a shot.