I find a Perl solution a bit more readable:

sub runcode {
  my @ret;
  while (@_) {
    my ($x, $c) = (shift, 1);
    $c++, shift while $_[0] eq $x;
    push @ret, "$c*$x";
  }
  return @ret;
}
[download]

If you want to golf this:

# 78 chars
sub RC {
#123456789_123456789_123456789_123456789_123456789_123456789_123456789
+_12345678
 my@r;while(@_){my($x,$c)=(shift,1);$c++,shift while$_[0]eq$x;push@r,"
+$c*$x"}@r
}
[download]

I'm sure it can be shrunk, but I'm kinda busy right now.

japhy -- Perl and Regex Hacker