18F1320 not capturing falling edge

[futz]

I wrote some 12F683 code to read an incoming servo pulse-train. Worked pretty well, but I have a small problem with it that I can't seem to find without a debugger. So I ported to 18F1320 (Junebug) and now I have a different problem that I can't find the solution to. It's probably something stupid I'm doing.

The ISR captures the rising edge of each pulse just fine, but doesn't ever catch the falling edge. Here's the setup and ISR code:

    ccp1con = 0b00000101;   //capture rising edge
    t1con = 0b00010001;     //Timer1 enable, pre=2
    t3con.T3CCP1 = 0;       //Timer1 is clock source for CCP
    rcon.IPEN = 0;          //disable priority interrupts
    pie1.CCP1IE = 1;        //enable ccp1 interrupt
    intcon.PEIE = 1;        //enable peripheral interrupts
    intcon.GIE = 1;         //enable global interrupts
...
...
...
void interrupt(void)
{
    if(porta.RB3){                      //rising edge detected
        start = ccpr1l;                 //store start value
        start |= ccpr1h << 8;
        ccp1con = 0b00000100;           //set to capture falling edge
    }
    else{                               //falling edge detected
        end = ccpr1l;                   //store end value
        end |= ccpr1h << 8;
        ccp1con = 0b00000101;           //set to capture rising edge
        flag = 1;
        if(end < start)
            pwin = (0xffff - start) + end;
        else
            pwin = end - start;
    }
    pir1.CCP1IF = 0;                    //clear interrupt flag
}

Any ideas? I can post the whole thing if necessary.

EDIT: Oh ya, this might be pertinent - the incoming pulse-train is from a 3.3V ARM7. The 12F683 had no problem capturing it, so I doubt that that's the problem, especially since it captures the rising edges perfectly.

EDIT2: Just noticed that porta.RB3 is never going low. That's why it isn't capturing falling edges. Hmm... Wonder if I inadvertantly turned on weak-pullups? Checking now...

EDIT3: Nope, that wasn't it. Added a pulldown resistor just in case, but it didn't help.

 

[futz]

Never mind. I'm an idiot! I've been checking PortA for a PortB input pin. Duh!

How embarrassing.