Java Applet crashes the Web Browser

We are using Internet Explorer version 5.5 to deploy a web based database application. I have written an enhanced JTable based Java applet as the backbone of the data exchange between the database and the users.

We have found that sometimes, the applet causes Explorer to crash. One day it will crash every time we access a page with the applet running, and other days it will run flawlessly.
Upon upgrading to any version greater than Java Plugin 1.3.0-C the entire applet crashes 100% of the time.

The applet itself is large, and is designed to be modular. It crashes mostly with the more complicated uses, but there are instances where it crashes just by being displayed in a web page.

Here is one of the test cases:

To start the page, load 'execute__startup.html'

You can ignore the name,description fields and the years, quarters,
months check boxes.


Then you change the levels number(1-9) the applet below should unlock
the corresponding rows of the table.
The unlocked out portions are white, and the greyed out portions are
locked.

Under the 'type' column, there are combo boxes with preset, edit, query
as the choices.

When you pick edit in the 'type' column, the 'source' and 'column'
columns become locked
When you pick preset in the 'type' column, the 'source' column becomes a
combo box, and the 'column' column becomes locked.
When you pick query in the 'type' column. The 'source' column becomes a
combo box with 2 items. When you select an intim in the 'source' combo
box, the 'column' then becomes a combo box with a group of atems as
well.


The crashing that occurs happen when we change the number of levels, or
change some of the combo boxes. It also crashes as soon as the page
loads.