Schema Browser Script tab for tables slow to generate DDL script.
Offending background query slow to execute:
Select user, table_name from sys.user_snapshots
There are options for Script tab that you can be changed in order to change the background queries needed to generate the script. Here is the option to turn off to avoid above query:
1. In Script tab of Schema Browser select Script Options icon
2. Select Tables tab, under "Other Related Objects" section uncheck Indexes checkbox and hit OK