Binary search with timestamps

Hello!
I've been using a binary-search like algorithm for an ordered array of 
time-stamps for ages. It works a bit like this (some code removed for 
clarity):


array - array to be searched, where time member is ordered
count - size of array
t - time
i - desired index where (array[i].time<t<array[i+1].time)


int i=count/2,n=count;
for(;;)
{
   n=n/2;
   if (t>array[i].time)
     i+=n;
   else
     i-=n;
   if (n<=1)
     return i;
}

It 'usually' works, but I can always find conditions where it doesn't 
and I'm not sure why. It works fine for sorted integers.

Noting the wikipedia page on binary search, it seems most programmers 
mis-program a binary so I've probably made the same mistake!

A linear search like this always gives me the right answer, but takes 
longer:


for(int i=0;i<count;++i)
{
   if (t>array[i].time && t<=array[i].time)
     return i;
}

I need speed though!

Thanks.