i dont think running that much that often will overtrain you unless you're brand spanking new.
i get cranky when im overtired and overtraining overtires me.
do you strnegth train? eat well? sleep well? take vitamins?
Running can trigger an iron deficiency and make you feel tired. If you're keeping a lower calorie diet, then that could be a possibility.
People get run down at different rates, if you're too tired and feel sluggish...then there's a reason for it.
Maybe your body is telling you to rest.
To me, lots of working out means that you are burning a ton of calories. If you don't eat enough to fuel the work outs, your blood sugar probably drops. Most people get cranky/irritable/tired with low blood sugar. (I am the queen of low blood sugar mood swings, haha). So, you might feel overtrained, but in reality you may just not be eating enough for our body (and mind) to keep balance. This all goes back to the over-analyzed subject of starvation mode and how much your body needs minimum daily. I'm not gonna get into that though, there are a million other posts where ya can read all about it :)
I think really being overtrained is more physical, such as joint and muscle pain, and thats when you really need to give it a rest. Being tired and cranky probably has more to do with how much youve slept and how much you've eaten. (anyone who wants to comment, go ahead, cuz like i said I am no expert!)
In general think that 25-30mins 3-4 times a week is almost a minimum reccomendation for cardio. Unless you push yourself too hard and start feeling physically beat up, I really dont think you have to worry about overtraining... and if you get crabby, eat! :)