We had this happen this morning. As soon as the breakfast bolus was given there was a blockage error. I looked at the tubing and the insulin had completely crystallized right above the luer lock in the tubing and also right above where the tubing connects to the site. This has never happened before. We've been trying to go for 3 days on the Cleo instead of 2 days -- this was day 3. We won't do that again. But it looks like it wasn't the site that failed, it was very obviously crystallized in the tubing. Why does this occur and how do I prevent it from happening again. I was relieved that the breakfast bolus actually worked -- he was 159 1 1/2 hours later. Because the alarm occured immediately after the bolus was completed.