mono error

[SibaN]

i get every time thes error any one know why i install last version from mono

if i start cash server is work but in 10 to 30 minute i get thes error

 

 

Unhandled Exception:

System.InvalidCastException: Cannot cast from source type to destination type.

at System.DBNull.System.IConvertible.ToInt32 (IFormatProvider provider) [0x00000] in <filename unknown>:0

at System.Convert.ToInt32 (System.Object value, IFormatProvider provider) [0x00000] in <filename unknown>:0

at System.Convert.ToInt32 (System.Object value) [0x00000] in <filename unknown>:0

at Cash_Server.Users.GetCashBalance (System.String username, Int32 userid) [0x00000] in <filename unknown>:0

at Cash_Server.Users.ProcessCashBalanceRequest (System.Byte[] packet, Int32 ClientID) [0x00000] in <filename unknown>:0

at Cash_Server.NetIO.Incomming (System.Byte[] packet, Int32 ClientID) [0x00000] in <filename unknown>:0

at Cash_Server.NetIO.OnDataReceived (IAsyncResult asyn) [0x00000] in <filename unknown>:0