if you put a redstone torch near a powered rail it will power 8 powered rails each direction and the one near it but if i put a torch near it it wont power the 10th powered rail. if i will put the torch near the 0th powered rail or the powered rail near it it will update but other places wont update that rail. i know its hard to think of so wee the pictures and comment what you dont understand.
Environment
win7 home edition 64 bit
intel i5 2500
gigabyte gtx 650 ti
java 1.8.0_25 32 bit
This issue is a duplicate of MC-957. It has been linked to the original bugreport.
Please search before reporting any bugs, as it's likely that one exists already.