possible reason for merge not working

Hi Guys,

working on a "merge" for 2 data frames.

Using the command:

x <- merge(annotatedData, UCSCgenes, by.x="names",
by.y="Ensembl.Gene.ID", all.x=TRUE)

names and Ensembl.Gene.ID are columns with similar elements from the x
and y data frames.

annotatedData has 8909 entries, so has x(as expected). x has columns
for UCSCgenes, but there is no data in them, all n/a, as if no match
exists.
This is not true as I can manually see and find many similarities

between the names and UCSCgenes columns.

I am wondering if there is any syntax error, or logical.