This webpage is not available error page when downloading purchased material from store

most of the time after a downloadable product is purchased from a store & when i try to download it it displays

This webpage is not available
The webpage at might be temporarily down or it may have moved permanently to a new web address.
Error 330 (net::ERR_CONTENT_DECODING_FAILED): Unknown error.

how am i supposed to use marketpress if i couldn't download products i purchased? please help