well, the ? right after the / is no problem on your site. this is a link sent from joomla. i use url-rewriting to shorten the url and didn't activate to append 'topic.html' after the last / so far. so the url i mentioned would look something like http://www.domain.xy/category/this-is-a-topic.html?key1=value1&key2=value2&key3=value3 when developement is done. but this does not reference the main problem. i used to send every possible kind of urls and only the urlencoded(url) was received in its full length by twitter. all none- urlencoded strings like the mentioned above end up after value1 and look like http://www.domain.xy/category/this-is-a-topic.html?key1=value1 . so the rest '&key2=value2&key3=value3' is getting lost even if the whole string is less than 140 chars long. i have no idea about that.
regards, tinobee