Multiple entry visitor denied

Hi
I would like , if possible a quick piece of advice, as I am a little bit lost.
To cut a long story short I have just been denied a multiple entry visa and a few of the explanatory reasons do not make sense.
I am a Romanian citizen living in the UK now. I have a 'yellow card" for about 2 months now which allow me to work for 20 hours a week as a student . I intend to study from sept 08 a BS in Biochemistry(have presented a proof of that , which also means I can extend my yellow card and upgrade to a 'blue card' which will entitle me full employment rights)
and I wanted to go traveling in South America for 2 months. I can get next-to-nothing Air Canada tickets but it means I have to go through Canada twice. So I decided to apply for a multiple entry.
The reasons given were:
-my travel history ( been to the UK in 2002 as a visitor, applied for a student visa and got denied but now I have a student registration certificate in UK,also I have traveled to Thailand and around Europe )
-my family ties in Canada and in my country of residence (should I have taken a letter from my partner that we live together and we have done for a year and a bit? his bank statements? a letter of marriage proposal??)
-purpose of visit ( I said I only want to be in Canada for 3-4 days, should it be more?? )
-my current employment situation (I work part time in a pub/restaurant due to the fact that I am only able to work 2o hours and )
I realise that from their point of view I probably do not qualify as the perfect candidate, but I am genuine and I do want to visit Toronto and also want to get to south america cheaper. Is there any chance in appealing against this at all?Is it possible that they've misunderstood me??
I would much appreciate any advice (besides the obvious one that I should avoid Canada) or what else can I do...

Kind regards
Carmen