importdata can't read files with strange extensions

I'm trying to use importdata to read a text file with a long extension: 'graphene.pdos_atm#1(C)_wfc#1(s)'

However, this fails with the following error:

??? Error using ==> importdata at 136 Unable to open file.

The problem seems to be associated with the extension, because importdata works fine if the '.' is replaced with another character. It seems like this is a bug in importdata. I realize that I could rename the files, but it would be desirable to have a solution from within MATLAB.

[Walter Roberson]

Which OS are you using?