JDBC SQLException, error code -691, error state 23000

Hello, I am newbie to informix IDS 9.4. I am trying to run a test jdbc program having multiple threads (2 threads). Trying to insert rows into multiple tables where some of the tables have foreign keys. I created a connection pool in my main function and passing the statements to the thread functions to be executed. The 'Connection' and 'Statement' objects are different instances (so no sharing there!) passed to each thread. (I used the IfxConnectionPoolDataSource and IfxDataSource APIs for pool creation) I am getting the following exception even though I verified that the foreign key column value is existing in the referred table. The same program works fine if I use just '1' thread. Is there something I need to set ? Is there something on the virtual processor settings that I need to change? (I am using the default values just out of install). Thanks in advance. ------------------- SQLException: Missing key in referenced table for referential constraint (root.r209_638). error code : -691 error state: 23000 at com.informix.jdbc.IfxSqli.addException(IfxSqli.java:3082) at com.informix.jdbc.IfxSqli.receiveError(IfxSqli.java:3396) at com.informix.jdbc.IfxSqli.dispatchMsg(IfxSqli.java:2259) at com.informix.jdbc.IfxSqli.receiveMessage(IfxSqli.java:2179) at com.informix.jdbc.IfxSqli.executeCommand(IfxSqli.java:721) at com.informix.jdbc.IfxResultSet.executeUpdate(IfxResultSet.java:305) at com.informix.jdbc.IfxStatement.executeUpdateImpl(IfxStatement.java:882) at com.informix.jdbc.IfxStatement.executeUpdate(IfxStatement.java:206)