Include lines dispappear

[Bil Click]

I am coding classic ASP pages in Visual Studio .Net 2003.
I file called counties_option.asp that just has a list of
options:
<OPTION VALUE="030">ANSON</OPTION>
<OPTION VALUE="040">ASHE</OPTION>
etc...

I then call this as an include file in several places in
a file called page1.asp like this:

<SELECT id="Select7" name="aCounty1">
<OPTION value="All" selected>All</OPTION>
<!-- #include file= '../common/counties_option.asp'-->
</SELECT>

This works OK the 1st few times, but after a while (I
have not determined the time period or cause) the
<include> lines disappears from the code!

I have other include files in this page that are stable -
only the includes in the <select> statements disappear.

Strange!