Clang (and gcc and comeau) accept the following invalid program:

static void test1(int *) { }

template
int *test2(const T &) { return 0; }

template
void test3(const T &t) {
test1(test2(t));
}

The statement "test1(test2(t))" is type-dependent all the way through to test1.
14.6.4.2/1 second bullet states:
"For the part of the lookup using associated namespace (3.4.2), only function
declarations with external linkage found in either the template definition
context or the template instantiation context are found."

Just to clarify, the first bullet is the one that governs from 14.6.4.2/1, but it too restricts to functions with external linkage.

test1() does not have external linkage. If we remove 'static' or change test1
to ::test1 (see the rest of the referenced section) then the program becomes
valid.

And this is fixed in C++0x, which says:

"— For the part of the lookup using unqualified name lookup (3.4.1), only function declarations from the
template definition context are found.

— For the part of the lookup using associated namespaces (3.4.2), only function declarations found in
either the template definition context or the template instantiation context are found. "

This was CWG issue 561, and I think it's reasonable to consider this a bug in C++98 rather than a bug in Clang :)