Thank you SOOOO much for your help with solving this problem

. Your suggestion was spot on but the placement was a little off. After doing a bit more research based on what you proposed, I found out that the solution was actually already in the datagrid code - have a look around the area of line 223.
## *** set variables that used to get access to the page (like: my_page.php?act=34&id=56 etc.)
/// $http_get_vars = array("act", "id");
/// $dgrid->SetHttpGetVars($http_get_vars);
I uncommented the two lines of code and changed them to
## *** set variables that used to get access to the page (like: my_page.php?act=34&id=56 etc.)
$http_get_vars = array("option", "Itemid");
$dgrid->SetHttpGetVars($http_get_vars);
and voila... it works fine now.
Again, thanks for your patience and your time. You are great.
I'm sure I'll need to tap into your expertise again sometime in the (very) near future so look out for me
