I read a couple of short articles about Lenin and Hitler met each other, and there is a picture, a drawing from Emma Lowenstramm - which's by the historians' opinion is most probably authentic - where they played chess in Austria in 1909. Here is a link to the article of the mentioned picture, thanks to neubau.
By historical timeline it could be possible since by then Hitler wasn't famous at all, he was in Austria, later after the WW1 he joined to DAP (Workers Party of Germany), by Lenin's side, then he was in exile from Russia because of failed 1905 revolution and he spent some time in Austria and Switzerland as well, and he attended to various communist congresses all around Europe.
Ideologically Lenin and Hitler had many common points. They both were socialist, they both were autocratic persons, they were both interested in politics.
Were they friends at any level? It seems from the articles I found by simple google search that at least they most probably met a few times.