error -410 after sweep

I'm programming a Keithley SourceMeter 2430 to run a sweep. Using similar code for non sweeping I've never had a problem. I'm running a sweep over the GPIB-USB-HS. First time through works fine but when I try to get a second set of readings I get the -410 Query interrupted error. If I restart my software I can again get one set of measurements before the error. I've been fighting with this for a couple of days and I need some help.

Here's my code.

Thanks

 Richard Hutchings

 ControlObjects.Keithley2430.Write("*RST")
        ControlObjects.Keithley2430.Write(":SOUR:CLE:AUTO ON")
        ControlObjects.Keithley2430.Write(":SENS:FUNC:CONC OFF")
        ControlObjects.Keithley2430.Write(":SOUR:FUNC CURR")
        ControlObjects.Keithley2430.Write(":SENS:FUNC ""VOLT:DC""")
        ControlObjects.Keithley2430.Write(prot)
        ControlObjects.Keithley2430.Write(startSweep)
        ControlObjects.Keithley2430.Write(stopSweep)
        ControlObjects.Keithley2430.Write(stepSweep)
        ControlObjects.Keithley2430.Write(":SOUR:CURR:MODE SWE")
        ControlObjects.Keithley2430.Write(":SOUR:SWE:RANG AUTO")
        ControlObjects.Keithley2430.Write(":SOUR:SWE:SPAC LIN")
        ControlObjects.Keithley2430.Write(trigCount)
        ControlObjects.Keithley2430.Write(":SOUR:DEL 0.1")
        ControlObjects.Keithley2430.Write(":READ?")
        Sleep(10000)
        readString = InsertCommonEscapeSequences(ControlObjects.Keithley2430.ReadString())
        VI = Split(readString, ",")