Created Unassigned: Attachments not downloaded [2396]

I have an email with 2 attachements and the name of the attachments are provided below
___cgregor_8-8-2014_16-46-41.pdf___
and
__32_More Direct TEST InvoiceCodingSheet (2).xls__

When I use, GMAIL for testing, I am able to download both the attachments.

But in production environmet it is downloading only 32_More Direct TEST InvoiceCodingSheet (2).xls.
And also, In the production environment when name of first attachment is changed cgregor_8.pdf, both the attchments downloaded without any issues.

Any thoughts on this...

Thanks in Advance...
Karthik