The Russian Civil War, where West faced off the Reds in direct military conflict, is an example of conflict due to ideology. Western beliefs in capitalism, democracy, and a free market economy were the complete opposite to communist ideology, which was about a one-party state where all was state-owned. A communist Russia would be a threat to the interests of the West. Although ideology was an important factor here, to say that this sole event was the origin of the Cold War would be ignoring significant events that occurred in following years.
In 1933, Roosevelt became president of the US and recognized the USSR. If ideology were so important, would the most prosperous capitalist country in the world acknowledge a communist Russia? When the US entered WWII in 1941, the two superpowers were allies - ideology was not a concern here; victory against fascism was.
Though it is true many problems resulted from the ambiguous agreements at Yalta, and along with change in leadership of two of the Big Three led to many disagreements at Potsdam, these were not related to ideology. Disputes over Poland were primarily because the USSR's fixation with security - it had been invaded three times in the 20th century through Poland and wanted it as a buffer state. Disagreements of Germany were due to the