pic16f887 PORTA simple or not?
When you do RA1 = 0; the PIC reads Port A, clears bit 1 in the value read, then writes the result back to Port A. This is called a 'Read-Modify-Write' operation.  

The PIC16F887 does not have separate addresses for I/O output and input, so when reading the port it always gets the pin state, not the output register state. Since you haven't disabled analog I/O on PORTA, all the analog input pins read as 0's. These 0's will be written back to the port's output register when doing a read-modify-write operation. 

You can set a pin to output mode while keeping the analog input, but to do bit operations on the port you should keep a 'shadow' copy of the output register in a variable, then change bits in the variable and write it to the port. Alternatively if you know what all the other output bits are you can simply hard-code them into the output value.

The same problem can occur if an output pin is pulled down by external circuitry (eg. a transistor or a 'large' capacitor) and can affect other operations such shifting bits or incrementing the value. If there is any doubt then it is best to avoid read-modify-write operations.