It sounds like youre binding Tab2 to a different DataSet than Tab1? Why? If you bind to both, updates in one will show in the other (but youd have to bind to the right row, or the updates on Tab2, in individual controls, may still show record 1).
A DataAdapter/DataSet is not syncd with the database. If you make changes they will not refresh automatically. You must do the refreshing. Each DataSet is also stored in memory separately and they are not syncd either. So even though they were filled with the same query, once that data was loaded into each DataSet, they became their own distinct repositories.
Id suggest using one DataSet in your case (seems right from the limited info you gave). If not, changes to one DataSet will have to be manually syncd with the other, either by merging one DataSet with another, or refilling one (or all) datasets from the database (a lot more network traffic).
-Nerseus