HTML IE issue: CF select one value where Cat are based on another CF


Using Internet explorer 8

I have a custom field where the Categories are based on another , using Internet explorer when users are selecting the values for both fields and clicking on Save Changes the dropdown for the dependant CF is reverting to (no value), however the value have been submitted and viewing the html source show the required value is selected.

For example:
I have CF called browsers with values
Internet Explorer

Another CF called versions with
Name: Category: as follows:
IE V 5.5 Internet Explorer
IE V6 Internet Explorer
FF V2 Firefox
FF V3 Firefox

When updating a ticket custom fields using internet explorer:
I can select Firefox from browsers and the versions drop down will show me FFV2 and FFV3 only - which is correct behaviour
However when I choose FF V2 and click save changes the versions dropdown is showing (no value) where it should be FF V2 , and the html source is indeed showing that the option where value = FF V2 is selected.

Has anyone else come across this and have they a fix, I understand that optgroup is new , however Internet explorer (version 8) should be able to handle this!?

Any suggestions?