I would like to be able to say that it's nothing more than a disagreement over the interpretation of certain biblical texts, but there's more to it than that. Behind and beneath our reading of Scripture, I'm sad to say, are theological beliefs that often govern what we allow the biblical text to say. The bottom line is that Arminians are already persuaded that the Calvinist view of divine sovereignty destroys human responsibility and makes God the author of evil. Likewise, Calvinists are already persuaded that the Arminian view of human freedom renders God contingent and transfers credit for our salvation from God to us. These convictions color how we interpret the Bible and which texts are given priority over others. Now, of course, both would loudly insist that they hold their respective positions because they believe that's what the Bible teaches, but all too often our interpretation is driven by a preconceived fear of where such interpretation might lead.
In addition to this, Arminians are concerned that Calvinism will undermine evangelism and the necessity of prayer. Calvinists are likewise concerned that Arminianism compromises grace and denigrates from the glory of God.
Needless to say, these are powerful and emotionally charged concerns that often derail the conversation and prevent us from looking at the text and allowing it to form and fashion our beliefs about the role of God in salvation.
(Excerpt from a Crossway interview with Dr. Sam Storms, who is coming to teach at Sojourn in mid-July. I think this is one of the best distillations of the Calvinism-Arminianism debate I've ever heard -- finally, something that's free from angry rhetoric and that assesses the problem honestly!)