This is a place where the browsers are not the same. The divs are inheriting the center attribute from the outside div in FF, but not IE.
The second div is also too large, since it is wrapping. FF decided to give it maximum width by placing it below the other div. This is part of the fluid nature of div.
Also, you are mixing css with the deprecated align attributes. This can cause unpredictable results.
Since you are already in a table, use the table to place the two parts where you want them. Tables always stick together in the correct order if all of the tags are present.