MIPS while loop error

Question

I am having some trouble with the following mips code:

    li $t0, -1
    li $t5, 0
    countNumberofVariables:
        addi $t0, $t0, 1
        beq $t0, $t8, endCount
        add $t1, $t0, $t9
        lb $t1, ($t1)
        li $t2, 10
        beq $t1, $t2, endCount
        li $t2, 13
        beq $t1, $t2, endCount
        li $t2, 97
        blt $t1, $t2, countNumberofVariables
        li $t2, 122
        bgt $t1, $t2, countNumberofVariables
        li $t2, -1
        stackScan:
            addi $t2, $t2, 2
            add $t3, $sp, $t2
            lb $t3, ($t3)
            beq $t3, $t1, countNumberOfVariables
            li $t4, 64
            bne $t4, $t3, stackScan
            addi $sp, $sp, -2
            sb $t1, ($sp)
            li $t1, 0
            sb $t1, 1($sp)
            addi $t5,$t5,1
            j countNumberofVariables

    endCount:
    move $a0, $t5
    li $v0, 1
    syscall

    j main

What I am trying to do is count the number of unique lower case letters in a string (address in $t9, length in $t8). The problem I am having, when running under SPIM 7.3 is that I get this error:

Instruction references undefined symbol at 0x00400108
[0x00400108]    0x11180000  beq $8, $24, 0 [endCount-0x00400108]; 87: beq $t0, $t8, endCount

The variables are:

$t0, outer loop counter
$t5, number of unique lowercase letters in string
$t1, the character at the current location in the string
$t2, random variable in outer loop, loop counter in inner loop
$t3, the character at the current location on the stack in the inner loop
$t4, random variable

note that the magic constant 64 is a sentinel value at the top of the stack.

EDIT: SOLVED. I changed label names to be shorter, which seemed to satisfy spim. Not quite sure what the underlying problem was, but if you are having a problem where there doesn't seem like there should be one, change to shorter labels