This sounds like a sick little Nile monitor. A healthy Nile hatchling should be able to catch crickets just fine. A healthy Nile hatchling should also be extremely concerned about its personal security and do whatever it takes to protect itself from giant hands desending from the sky to grab it.
Note that with age, some Niles will mellow out. I have had one relatively trusting Nile, but many that were unhandleable without a major fight.
Advice? First, get it to a vet. Second, make sure the temperature is appropriate (45 to 55 degrees C basking spot, 25 degrees C ambient). Give it a substrate that it can burrow in - a monitor burrow should provide security, humidity, and protection from temperature extremes. Rob Faust's book on Nile monitors is good (although it focuses more on ornate monitors than the true Niles). You can also visit my website at
http://pizards.com/hbd/nile.html where I have a page written about this species.
Good luck,
Luke