Apparantly 2038 is inability to connect to server.
See some suggestions at https://getsatisfaction.com/booksonboard/topics/adobe_digital_editions _gives_me_error_2038_when_i_try_to_download_how_do_i_get_my_book
for example, temporarily turn off your firewall.
Someone else says it may be a version conflict. http://support.diesel-ebooks.com/kb/article/troubleshooting-questions/ i-receive-error-2038-in-adobe-digital-editions
It could be that the AdobeID registration has got confused; it does sometimes.
Try clearing it using ctrl-shift-D to ADE, restart ADE, and reapply your old registration.
Then see if you can open the book.
If you need to reinstall ADE, v1.7.2 is probably your best bet. There are lots of issues with 2.0, especially on older machines.
Version 1.7.2, it is a little difficult to find, available on Adobe site for Windows and for Mac.
http://helpx.adobe.com/digital-editions/kb/cant-install-digital-editio ns.html
The forum software is sometimes corrupting the link above. There shouldn't be a blank in 'editio ns.html'. The following redirects to the same page: http://tinyurl.com/diged172