Hi,

There may be no of reasons why it is happening.

1. Do you have indexes on those tables.

2. When did you update your indexes and statistics last.

3. Do you have any other processes or blockings while select or update is going on these tables

4. Did you study the query plan . you can find out what exactly is happening in your query plan if you dont have any blockings etc..

Thanks

Chandra Mohan N