llDetectedName problems

I've been trying to write code that determines whether a name typed in a given channel is a substring of a nearby (10.0 units) detected avatar name.

the problem is that llDetectedName(i) (for a given index i) is always giving -1 as a return value even when the substring is correct.

So that:

// start of for loop
//...
...

llSay(0, "Avatar = " + llDetectedName(i));
index = llSubStringIndex(llDetectedName(i), "Fred");
llSay(0, "index = " + (string)index);

Will always give an index of -1. Even when, say, Fred Bloggs is detected.

If I replace with

index = llSubStringIndex("Fred Bloggs", "Fred");

Obviously the string function works and returns 0.

What is the issue with llDetectedName?

I just tried setting a string variable to llDetectedName(i) prior to using the string function and it's ok now.

wtf?

I was having a similar problem with llListFindList last night. I switched to using strings and it worked right. It didn't break for all lists, just some. (and I verified that the sublist was in the list too.)

I don't know. Maybe something was up behind the scenes. Or maybe it was a memory issue.