This problem may arise during gameplay on nvidia GeForce GT 640M while playing older games.If you get this problem in which a game crashes suddenly then try running it in compatibility mode.You can access compatibility mode by right clicking on the game's exe file and clicking properties.Then you will see a compatibility tab on the top.Click it and check "Run this program in compatibility mode for" and choose the highest possible operating system. system overheating can be an issue.If the notebook gets overheated shut it off for few minutes and let it cool down properly before resuming gameplay.Use good quality thermal pads for notebooks and thermal paste for CPU heatsinks in desktops.use HDMI cable instead of normal display cable if your monitor supports HDMI interface.check the resolution of the game which you are playing.If it is on low resolution then increase the game resolution by going to settings.Make the resolution as much as possible.To enjoy any game a condition arises that whatever you see on the screen should have sharp and real graphics like the real world if you have invested money in this graphics card.But it can happen when you see blurry graphics on the monitor screen this will totally end your gaming experience as the gaming detail would not be clear and you may not like to play it at all.For fixing blurry graphics on nvidia GeForce GT 640M check the following things.
The above steps will solve the UBYTE4N vertex data problem.This problem may or may not arise on notebooks.ΔΆ.Sluggish,Blur And Rough Gaming Graphics
first of all install the correct and latest driver.The driver can be found in the installation disk came with the graphics card.UBYTE4N vertex data problem arises when the graphics card doesn't support the game totally which is too much for the onboard chip.The UBYTE4N vertex data problem is common with Intel chips.If you are getting this problem either with notebook or desktop even after inserting the graphics card in proper slot then check the following things.
If you are getting this problem then your notebook doesn't have the right driver installed.