Passing in Global Variables in Python

tl;dr: Global variables have nothing to do with this; it is almost certainly that you are passing a string instead of an int as your length parameter. Your code had a lot of redundancies.

Your code has a number of obvious problems, both stylistic and substantive:

def getNGramBeginsWords(nGram, length):
    # dict is the name of a builtin function, which you are confusingly overwriting
    # dict = open('/home/will/workspace/Genie/src/resources/TWL06.txt', 'r')
    wlist = open('/home/will/workspace/Genie/src/resources/TWL06.txt', 'r')
    nGram = nGram.upper()
    words = []
    for line in wlist:
        # an empty string evaluates to False in a binary context; also no need for those brackets
        stripline = line.strip().upper() # you keep doing this; I added the upper here.
        # you don't need this if, because you immediately test length
        #if stripline: #I know I changed this, but you only refer to the stripped version below 
        # pipe | is bitwise OR. I bet you don't want that
        if len(nGram)>len(stripline) or len(stripline)!= length:
            continue
        # s = stripline[:len(nGram)] #you only use this once
        # you don't need to check that stripline is of length again; you already did that
        # also, you can just use `endswith` instead of slicing
        if stripline.endswith(nGram):
            words.append(stripline)
    return words

And, without comments:

def getNGramBeginsWords(nGram, length):
    wlist = open('/home/will/workspace/Genie/src/resources/TWL06.txt', 'r')
    nGram = nGram.upper()
    words = []
    for line in wlist:
        stripline = line.strip() # you keep doing this
        # you can merge these two ifs
        if len(nGram)>len(stripline) or len(stripline)!= length:
            continue
        if stripline.endswith(nGram):
            words.append(stripline)
    return words

Merging the two adjacent ifs:

def getNGramBeginsWords(nGram, length):
    wlist = open('/home/will/workspace/Genie/src/resources/TWL06.txt', 'r')
    nGram = nGram.upper()
    words = []
    for line in wlist:
        stripline = line.strip().upper() # you keep doing this
        # you can merge these two ifs
        # also this renders the comparison of ngram and stripline lengths redundant
        if (len(stripline) == length) and stripline.endswith(nGram):
            words.append(stripline)
    return words

Now, let's look at this last version - funnily enough, you never actually perform a numeric operation on length. Given that length is supposed to be a number, you might like to force it to a number; if it can't be converted, you'll get an exception.

def getNGramBeginsWords(nGram, length):
    wlist = open('/home/will/workspace/Genie/src/resources/TWL06.txt', 'r')
    nGram = nGram.upper()
    words = []
    length = int(length) # force to an int
    assert isinstance(n, int) # or do this if you prefer to get an exception on all invalid input
    for line in wlist:
        stripline = line.strip().upper() # you keep doing this
        # you can merge these two ifs
        if (len(stripline) == length) and stripline.endswith(nGram):
            words.append(stripline)
    return words

And finally, you never actually close the file explicitly. You'll have it hanging around for a while. It's better to use the with construct to close it automatically:

def getNGramBeginsWords(nGram, length):
    with open('/home/will/workspace/Genie/src/resources/TWL06.txt', 'r') as wlist:
        nGram = nGram.upper()
        words = []
        length = int(length) # force to an int
        assert isinstance(n, int) # or do this if you prefer to get an exception on all invalid input
        for line in wlist:
            stripline = line.strip().upper() # you keep doing this
            #you should be using `endswith` instead of the slice
            if (len(stripline) == length) and stripline.endswith(nGram):
                words.append(stripline)
        return words