and it was fine, then I am not sure, possibly it is a problem with your updated client, and someone more knowledgable about the PC client hopefully can help you...
But, here are some things you can do to make it run faster:
1.) Switch into 16 bit colour from 32 bit, it will help a lot and I really didn\'t even notice a graphics change when I did this to my client.
2.) Set Adaptive distance in the options to something even as low as 50. The game will not look as good, but it will help
3.) Turn off all transparency in the in-game windows, this normally eats up RAM.
4.) Turn off the sounds if need be.
Also, for the devs to help you, you will need to give them your graphics card details, it is possible you need to download the latest drivers for yours. Also, what is your processer speed?
Hope this helps,
Xirius