Problem - User & Group Accounts

[Reader1]

I'm having a problem adding users/groups to my database.

If I try and add a user it comes up with a message 'Couldn't update;
currently locked by user 'me' on Machine 'my machine'

Upon checking the user list, it does actually add the new username but it
fails to assign any group even the Users group.

If then I try to add the username to a group the same message again displays
'Couldn't update; currently locked by user 'me' on Machine 'my machine'

What could be the problem here ?

Is the .MDW file corrupt ?

Do I need to recreate it ?

My account has Admin privileges so I can't see the problem here and I've
never had this problem before.

I assume that it's OK to add users/groups while the database is in use by
other people ?

Thanks for reading.

 

[Reader1]

I'm having a problem adding users/groups to my database.

If I try and add a user it comes up with a message 'Couldn't update;
currently locked by user 'me' on Machine 'my machine'

Upon checking the user list, it does actually add the new username but it
fails to assign any group even the Users group.

If then I try to add the username to a group the same message again
displays 'Couldn't update; currently locked by user 'me' on Machine 'my
machine'

What could be the problem here ?

Is the .MDW file corrupt ?

Do I need to recreate it ?

My account has Admin privileges so I can't see the problem here and I've
never had this problem before.

I assume that it's OK to add users/groups while the database is in use by
other people ?

Thanks for reading.

Created a new database and MDW file, imported all objects from original
database and recreated the groups and users.

All is well now but still don't know what happened !