Opera 7.x Win98 div positioning

I'm trying to use the following html/css to create a box with a left
side and a right side. It's not complicated and it works well in
several versions of IE on Win2k and Win98 and Opera 7.11 on Win2k.
However if I try it on 7.x (it may not be 7.11 but it is 7.x, I can't
verify which it is right now) on Win98, it not only crashes Opera but
invariably it will crash the entire OS after a few minutes. So what I
want to know is, is there something wrong with my html/css or is this
some strangely isolated compatability problem?
Regardless of that answer, is there another way to achieve this same
effect? What I would LIKE to do is have a fixed position left side
div but that isn't supported by IE yet so I tried to do it this way.
I'm also trying (TRYING) to avoid using frames or tables.

here is the short bit of html:

<div style="position: absolute;
width: 85%;
left: 7.5%;
height: 30%;
top: 7.5%;">

<div style="position: absolute;
width: 30%;
left: 0;
height: 100%;
top: 0;
background: #00F;">left side</div>

<div style="position: absolute;
width: 70%;
left: 30%;
height: 100%;
top: 0;
background: #FF0;
overflow: auto;">x<br/>x<br/>x<br/>x<br/>x<br/>x<br/>x<br/>x<br/>
x<br/>x<br/>x<br/>x<br/>x<br/>x<br/>x<br/>x<br/>
x<br/>x<br/>x<br/>x<br/>x<br/>x<br/>x<br/>x<br/></div>

</div>


Thanks
k