Ubuntu 14.04 clients get Hash Sum Mismatch error when running apt-get update

Problem

In the last few days, clients running HipChat4 on Ubuntu 14.04 are getting the following error when trying to run an apt-get update:

W: Failed to fetch 
https://atlassian.artifactoryonline.com/atlassian/hipchat-apt-client/dists/trusty/main/binary-i386/Packages 
Hash Sum mismatch
E: Some index files failed to download. They have been ignored, or old 
ones used instead.

Environment

Systems running Ubuntu 14.04 desktop, 64-bit

Steps to reproduce

On a 14.04 desktop with the hiphchat4 client installed from our repositories, run:

'sudo apt-get update'

Actual results

Error above is seen and can't be cleared by running such commands as:

rm -rf /var/lib/apt/lists/*

apt-get update

Expected results

No Hashsum mismatch errors from apt-get

Notes

Not sure if this is related, but, the apt repositories were recently fixed to take care of a "No Hash entry in Release file" error for systems running Ubuntu 16.04

https://jira.atlassian.com/browse/HCPUB-369