Do you recommend conversation courses?

Hi

I don't have a problem in English at all (I did vey well in TOEFL), my problem is actually is SPEAKING in English. My vocabulary is quite good but sometimes when speaking I feel that words just run out of my mind.. and as a graduate student this is really embarrassing for me. I lack the courage to start a conversation and I find it difficult to express my opinion and thoughts in a long talk especially in front of many people.... a head-to-head conversaton is much easier. What makes it worse is that a considerable part of my study depends on giving presentations and seminars and imagine how tough it is in my case!! Moreover, my thesis defense is quite soon. So, my question is: are conversation courses beneficial in my case? Do you recommend them?

Waiting for replys.... thanks