Input to "disabled" INT1 halts execution

87C51RA+
Trying to use P3.3/INT1 as an input.

I set EX1 = 0; at the beginning of main(), which should disable INT1. EX1 is not referenced again, and remains =0.

Whenever I pull the P3.3/INT1 pin low, the program slows down to a crawl . . . when I let the pin go high, the program picks back up to normal speed.

Here is one place that I am seeing it happen:

while (sec < MSEC_100 * 2) {
kick_dog();
}

void kick_dog()
{
EA = 0;
CCAP4L = 0X00;
CCAP4H = CH;
EA = 1;
}

As you can see, global enable is used to toggle interrupts on and off. My impression is that the EX1=0; instruction should keep the INT1 disabled whether the EA global bit is subsequently toggled or not, but all that I can figure is that the interrupt IS active and causing the slowdown.

EX1 and EA are defined in #include <reg51f.h>

What am I missing here?

Thanks,
Scott Kelley