Error: conversion, reading from file

[Michael P.]

I've having some trouble reading from a file.
I am trying to read a list of high scores, each on a separate line, like this:

440
0
0
0
0

But with my code, I get an error saying: Error: conversion.
Code:

//Load high scores
char[] file;
int[] highScoreList;
int nextScore;
file = cast(char[])read( "highscore.txt" );
for( int i = 0; i < 5; i++ )
{
	nextScore = std.regexp.find( file, "\n" );
	highScoreList ~= toInt( file[ 0 .. nextScore ] );
	writefln(highScoreList[i]);
	file = file[ nextScore .. $ ];
}

The output I get is:
440
Error: conversion

The high scores that are printed above is what is in the file.
I am using DMD1.046 with Phobos.