Yes, even after World War One, there was still much racism left, which would cause the ethnic clashes that occurred. One great example is what happened during the holocaust, where an entire race of people was going to be eradicated until America and other countries stepped in and stopped it.
I do not believe the cleansing clashes in Europe in the mid-1990's were lingering effects of World War I. Ethnic cleansing has been a part of human history probably longer than we are all aware and it is still a problem in today's worlds. I do not think we can directly attribute happenings in the 1990's to WWI, especially when WWII happened in between time.
World War I is not the reason for ethnic the cleansing clashes in Europe in the mid-1990s. The reason these cleansings happened is because the borders for these countries were drawn arbitrarily after the first world war with no regard for ethnic or religious make of the areas in question. These ethnic group never get along and only communist governments kept the peace until the 90's.
The genocides of the late 20th century were not related to the cases in the beginning of the century. Although the crimes are the same, they are not inter-related. So much time had passed between the two events, it is hard to identify how they could be conneced to each other.
No, I do not think that the lingering effects of World War I caused many of the ethnic cleansing clashes in Europe in the mid-1990s, because there have always been clashes in Europe. The ethnic clashes in Europe go back hundreds if not thousands of years. World War I was a very large ethnic skirmish, but it was only one of many.