I mined in some other pool and got some coins. When I switched to another pool, I found that my account's address was changed and the balance was 0. Later I did not try to exit the pool on a non-zero balance. So, I switch the pool, the coins that were mined before will not be lost, right?
Are you using the latest version >= T13.793? There was a bug with different addresses in older version. Now it is fixed. If you connect to another pool the address should remain unchanged and the balance too.
Tried this already, adress stays the same and balance was also ok...