Cant upload zip file themes

I have tried to upload paid for themes from ‘Elegant themes’ but cannot do so:
The theme is called ‘elist’

after the zip file gets compressed onto my Mac it gets split like this and so cannot download the ‘elist folder’:
changelog.txt
comments.php
css
epanel
footer.php
functions.php
header.php
home.php
images
includes
index.php
js
lang
license.txt
listing_content-single.php
loop-page.php
loop-single.php
page-blog.php
page-contact.php
page-full.php
page-gallery.php
page-login.php
page-search.php
page-sitemap.php
page-template-portfolio.php
page.php
psd
ptemplate-submit.php
sampledata
screenshot.jpg
sidebar.php
single-listing.php
single.php
style.css
taxonomy-listing_category.php
taxonomy-listing_tag.php

so i cannot upload it to the WP dash
so then i copied the zip file onto the desktop
then this error message comes up:

The uploaded file could not be moved to /hermes/bosweb26a/b167/ipg.reallyusefulworldcom/wp-content/uploads/2011/12.

Internal Server Error
The server encountered an internal error or misconfiguration and was unable to complete your request.

Please contact the server administrator, [email protected] and inform them of the time the error occurred, and anything you might have done that may have caused the error.

More information about this error may be available in the server error log.

I have tried for hours to upload these premium wordpress themes but am getting nowhere!
please advise asap
thanks
Mr Nollid