Updating records with Excel Plug-In not working correctly?

Hello everyone!

I am currently trying to update all of our phone numbers (1500) in the contacts module to make them uniform.

I tried using the SugarCRM Excel Plug-In for Excel 2010 64-bit (query, Contacts->last_name->isNotEmpty), but when I change the values in "phone_work", select the whole column(from first to last record, without column titels) and right-click "update in Sugar" the only thing that gets updated (according to my activity stream at least) is the column "date_modified", but no the numbers.

When I tried selecting the entire rows and use the update from the dropdown menu nothing happens at all.

I tried testing both functionalities: I created 10 dummy contacts and used the query to get them listed and performed the same changes as descibed above with both methods and BOTH WORKED!

Is there a limit as to how much records can be updated at the same time? Is the update functionality disabled for large queries/lists? I am really confused :-?