I've the following problem. From a client application I connect (ODBC) to a Firebird 1.5 database. But on one pc after issuing a SQL select statement the client hangs. This only happens on some places in the application and happens all the time (I can reproduce this). But it's only on one of the four pc's. The other pc's are working fine.
It used to work fine on this pc too.

I isolated a piece SQL from the application and made a small application with only this query. I tried to change the query to find out if there was a point at which it would go wrong.
I discovered that if i remove some columns from the select it works ok (I get results). I tried to add columns one by one and suddenly the client hangs (no results). I couldn't explain in which situation it would go fine.
Is there maybe some limit on resultsets? But why would it only occur on this pc.
I have no idea where to look for a solution. I tried turming off firewall and laying with locking-levels etc.

I have the same application running at two customers. At both locations one pc has this problem.....

Can somebody put me in the right direction to look for a solution??