Sharepoint Services 3.0

Hi,

I am using basic installation of WSS 3.0 on SBS 2008..Everything seems to be working fine except :

For instace i've a document in the library named test.docx
User X has logged in with member's  group..and has checked out this document...


Now when User Y loggs in with same member's group..and watches the document test.docx is been checkout to User X..
Even though User Y opens the document...when user Y clicks on edit a document...It is prompted by 3 options, with a dialog box :

File in use:
Do you want to:
.Open as read only
.Create a localy copy and merge your changes later
.Recieve a notification when original copy is availaible..


Lets say User Y has clicked on option 3rd...which is
.Recieve a notification when original copy is availaible..

Now the problem is when User X Check In a test.docx document...with some comments..User Y still doesnt receive any notification about it that it is now availaible for editting...


Any help would be greatly appreciated..

Regards
Salim...