Float & Clearing Problem

I have 2 columns. Both columns are made up of numerous stacked divs. Left Column is set with a float of left, and right with a float of right. It all works, until one side is bigger than the other:

[1][2]
[3][4]
...[5]

#5 moves over on the left column (under #3 and next to #4) when the right column is longer.

How would I fix this?

Hello Erindesign,
Does .left {
float: left;
clear: left;
}

.right {
float: right;
clear: right;
}
fix it for you?

If not, copy/paste your code here so we can have a look.