file is corrupt?

I've heard that there are times during the creation of a package that this can happen. It's working fine now... or if it's not, you should follow up with the package management system or the drush project.

I see #499884: checksum errors on some modules in drush dl had a long-running drama about this. If you haven't already upgraded to drush 5, I sure encourage you to do so.

$ drush dl --package-handler=wget examples
Install location /Users/rfay/workspace/d7git/sites/all/modules/examples already exists. Do you want to overwrite it? (y/n): y
Project examples (7.x-1.x-dev) downloaded to                         [success]
/Users/rfay/workspace/d7git/sites/all/modules/examples.
Project examples contains 35 modules: xmlrpc_example, vertical_tabs_example, trigger_example, token_example, theming_example, tablesort_example, tabledrag_example, simpletest_example, render_example, rdf_example, queue_example, pager_example, page_example, nodeapi_example, node_example, node_access_example, menu_example, js_example, image_example, form_example, filter_example, file_example, field_permission_example, field_example, entity_example, email_example, dbtng_example, cron_example, contextual_links_example, cache_example, block_example, batch_example, ajax_example, action_example, examples.