Students will need their maintenance funds (years tution plus expenses) in their bank accounts 28 days prior to applying. It is not 3 months though, which applies to other visas that are part of the points based system.
The bit we were bantering about is that both myself and ksand were saying the same thing, though I thought she was saying something else because I read her post too quickly.
But it also says that the 28-day rule doesn't come into effect until 1st June 2009 (as per Amy's second post, the source of which is the visa guidance on the UK visa site), so if she applies before June 1st, it looks like she won't need to worry about the 28 day rule.
The only problem that you might have, Amy, is that you may not be able to apply before June 1st due to the rule that visas can only be post-dated by 3 months. If your course starts in September and you will be travelling then, the earliest you can apply for the visa is June. However, you are allowed to enter the UK up to one month before the start date of your course, so you will be able to apply 3 months before this date.
Looking at your previous posts, I see you will be studying at LSE. The 'Fall' 2009 term at LSE begins on October 1st, which means that the earliest date you can enter the UK is September 1st. Therefore, the earliest date you can apply for your visa will be June 1st.