I just put new line on my reals. I went fishing and on two of the reels, the line broke inside the reel.  What causes this?

Could be a couple of things. What type of line are you fishing? Sometimes fluoro gets quite brittle, and even the slightest knicks can make it snap. The other thing it could be from is a backlash. If you're fishing mono, that's a different story, it's usually not to brittle.

A small loop or kink forms in the spool that rubs the inside of your reel when you cast until it severes.  A lot of time you  can can hear it rubbing on a hard cast...zzzzzzzz....and then silence as your lure sails into no-man's land.  That is why it is important not to be lazy when you get a small loop in your spool and take care of it.  Regardless...even the most seasoned angler will have this happen; some of the loops or kinks are so small they are undetectable until your lure sails into the sunset .

I hate the no-mans-land lure sail.............I think The_natual has it on the head.  Kinks.  Those rotten things will get you if your line is not spooled with enough tension. :'(

I hate the no-mans-land lure sail.............I think The_natual has it on the head. Kinks. Those rotten things will get you if your line is not spooled with enough tension. :'(

That and anything that says Vanish on the package.

I hate the no-mans-land lure sail.............I think The_natual has it on the head. Kinks. Those rotten things will get you if your line is not spooled with enough tension. :'(

That and anything that says Vanish on the package.

x100--I've used this "joke" before, but that crap tears up just coming through the water