Bicep help

I have recently started training regularly and am finding on days when I train back and biceps, after doing my back I find it almost impossible to curl even light weights. There is no burning or aching in my arms but they refuse to move. Is this bad? Or are my biceps just tired

The biceps will be involved in compound exercises so you'll probably be hitting them when you're doing your back exercises.  You don't necessarily need to do the isolation exercise.
 
What movements do you do on that day and what set/rep scheme?

Thanks for the reply. I am doing seated rows, pull downs and dead lifts. And 4 sets of 8-10 reps

It's not unusual for the biceps to be very tired after a back compound session, but to have no movement at all is a new one on me.
 
Two things initially come to mind:
 
1. Get your form sorted out on your rowing / pull down exercises and make sure you're engaging the lats properly and getting the arms out of the movement. This will mean lowering the weight and concentrating on keeping the shoulders low, chest forward and really pulling the shoulder blades together.
 
2. There's something wrong if you can't curl at all that needs checking out.

It's hard to give the correct answer without really know loads of other details buddy.

I would suggest getting someone to watch you and make sure your form is hitting your lats with the rows and pulldowns these are exercises that are easy to use the bicep which take over the movement.

Try training the biceps on another day. if your new to training it will come with time dont rush things. my biceps burn out very fast also and I've been training 23 years.

Just read your 1st post again. No it's not bad mate. I would just say yes your biceps are tired, nothing to worry about at all.

If you have a instructor do your routine I'm sure if you explain what your feeling they will sort it for you.