Dammit i got Ninja'd out of doing my job,well judging by the information you provided i'd say it is a graphics issue which can be solved by either updating your graphics drivers or toning down your settings in game. 1755 has a nasty habit of sapping a lot of RAM which can diminish performance greatly so try the program Alan suggested, it helps by stopping useless programs running in the background so all the RAM can focus on the game only.
Well i have some good news for you. It happened again. Again when entering a city just before the menu popped up. Shader Error: Out of Memory.
I have 6gb of ram.
4870x2 with 2gb of ram
Memory? I don't think so. Actually I had the same issue with Floris mod that I tried and it would give me the exact same error before even loading the menu screen. What actually fixed it was that one of the Mod devs (i think) found it to be the sounds.txt file that was causing it... yeah doesn't make any sense to me either. Anyway downloaded the fixed sounds.txt file for that mod and it has run smoothly ever since.
So even though it has come up with an error that makes it seem like it should be a video problem... it might not be? And why would it make this sort of error when going into a city? As far as i know city menus are not very graphics intensive.
I will wait for the next 1755 version to come out and if it is still doing it then I will try setting it to DirectX7 if I can bear the ugliness long enough to see if my problem really is a video problem.
I will not roll back my video drivers. As much as i would love to play this mod for a good long time I will play something else before I do that as other games I have benefit from the current version i have.