dlmread giving error while reading a .csv file

I am trying to read a .csv file using dlmread command but it is giving an error on running it. This is how I used this command to read the file.

dlmread('filename.csv',',',0,0);

The error it is producing is,

usage: unique (x) or unique (x, 'rows')Undefined function or variable 'toascii'.

Error in dlmread (line 147)
  throw(exception);

It started giving the error from past few days only don't know why. If anyone can help, it will be great.

[Walter Roberson]

I suspect the error is happening while executing setdiff()

I recommend

dbstop if caught error

and running the code. When the error occurs in unique, dbup to see exactly where it is being called form and what the arguments are.

My guess: that you have your own find.m function.