Have to go into court to show just cause for Child Support?

I have always worked hard to make sure that my kids had everything and my ex-wife never had to buy them anything. I have payed child support on time every month until 6 months ago. I had to quit working in early 2008 because of my diabetes, arthritis and have congestive heart failure. I worked on cars for as long as I could physically and sent in every spare dime that I had into child support even if it was not the court ordered amount for the past 6 months. I applied for disability 2 months ago since I cannot work. On top of what I send to CP I have always bought their clothes, made sure they had anything that they ever wanted and needed since my ex and I split up. My ex never bought them anything using the CP. I am now $1700 behind and I received a court summons for a show of cause order to go into court to explain why I didn't pay anything last month. CP has reported that I still work for my old employer in this summons and dont pay the CP just because I dont want to. Why the worker put these things in the order just because my ex says so without any real proof? Is that legal? Besides the fact that my ex use to have an aunt that worked for Social Services. What's also really irritating is that she filed outrageous domestic violence charges on the 20th of last month (which she never even showed up for court for and which also made the 3rd time in 3 years) and then had SS do this order on the 21st. Are there any factors here that will help me in court on Monday?