I was able to reproduce this issue you are having with Powerstore in regard to the SKU.
I have logged a bug in our bug base and the fix should be included in a future dot release. Meanwhile i have listed the instruction on how to fix this issue which it should be straightforward:
1. open the Products_Update.php page and replace line 240 with this line:
$query .= ((isset($_POST['AllSKU']))?"ProductSKU='".$AllSKU."',":"");
This should fix the SKU issue.