Adlink USB 7250

Hello Forum,

I know this is not an Adlink forum, but can anybody help me?

I am using an Adlink USB7250 DAQ together with labview 12.

I'm trying to control a relay with the adlink in setting the DO Port to high and after 2ms change it to low. This works fine, but if I put a for loop around it I get an error  "No channel is enabled for this operation.". The error occours after the first run.

Does anybody have an idea?

Thanks