Fatal error: curl_init() - Unable to login.

Hi there,

I have enabled the module and attempted configuration (admin/config/search/wordstream) but get this.

Fatal error: Call to undefined function curl_init() in www.example.com\sites\all\modules\wordstream\class.wordstream.inc on line 124

For the login I could not find any details so I just used my login for the wordstream site.
Username: email@example.com
Password: password1234

Secondly, admin/structure/wordstream produces,

Notice: Undefined variable: analysis in wordstream_keyword_stats_report_page() (line 132 of www.example.com\sites\all\modules\wordstream\wordstream.module).
Notice: Undefined variable: analysis in wordstream_keyword_stats_report_page() (line 140 of www.example.com\sites\all\modules\wordstream\wordstream.module).
Notice: Undefined variable: analysis in wordstream_keyword_stats_report_page() (line 146 of www.example.com\sites\all\modules\wordstream\wordstream.module).
Strict warning: Only variables should be passed by reference in wordstream_keyword_stats_report_page() (line 146 of www.example.com\sites\all\modules\wordstream\wordstream.module).
Notice: Undefined variable: analysis in wordstream_keyword_stats_report_page() (line 150 of www.example.com\sites\all\modules\wordstream\wordstream.module).

A search produces,

Fatal error: Call to undefined function curl_init() in www.example.com\sites\all\modules\wordstream\class.wordstream.inc on line 124

I am trying to use the SEO Tools module but after the errors I tried again without other modules installed only (Minimial 7.10, Admin Toolbar and Demonstration).

Any help is much appreciated,
Thank you in advance,

Phil.