I had the same issue and I was looking for an answer, and I have seen that many people tried the cookie thing that did not work for me, or htaccess....anyway...here it goes what I did.
I was debugging the login.php file to try to see where the issue lies...and I am still trying to figure this one out (I am just gaining experience interpreting someone else's code), but I discover at least something to make it work while I was debugging. Before I continue with the solution...yes my debug method consists of writing a bunch of "die (here);" sentences

Anyway, go to the admin/login.php and search for this code:
if($result == TRUE) {
$_SESSION['ccAdmin'] = $result[0]['adminId'];
// update no logins
$increment['noLogins'] = "noLogins+1";
$result = $db->update($config['dbprefix']."CubeCart_admin_users", $increment, "adminId=".$result[0]['adminId'],$stripQuotes="");
if(isset($_GET['goto']) && !empty($_GET['goto'])){
header("Location: ".urldecode($_GET['goto']));
} else {
header("Location: ".$GLOBALS['rootRel']."admin/index.php");
}
Now place this right after this code and before the else statement
die ("here");
I know it is NOT A DEFINITE CLEAN solution but at least I was able to get in the admin area. Once I know what is going exactly, I will return to you!
Hope it helps!
Clauz