Please change the onmousedown with onclick. The mouseup changes the focus and thus may cause issues. I believe that there has been some change in FireFox related to focusing elements after mouse events, yet I cannot confirm this with 100% certainty. Also, when opening a RadWindow from a Radwindow you only need to set a small timeout when calling radopen() or show(), you do not need setActive() in this case. This is shown in this help article
This means that I suggest you change the following lines:
wnd = window.radopen(
and in ProductDetails.aspx
"cursor: pointer; white-space: nowrap;"
. . . . . .
Similarly, you can replace the other onmousedown handlers with onclick, as it is a more reliable event.
Once I did this things were working properly with me (a screenshot is attached, as well as the two modified pages).
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