Of course there is a way to edit the file. There are lot's of ways. Use nano, or vim etc. Further unless you need to use the vesa settings then it won't make much sense to edit it. Might be best to post info on your laptop, especially your gpu. Do you have a driver for it? Etc. These types of things are hard to diagnose without proper information. You will also need to look at ubuntu 8.10 as well as the kernel version to see if there are reported problems.