Last September, HTC's integrated Twitter client Peep stopped working because Twitter's switch to a new authentication method called OAuth. Three days later the app started working again, being allegedly fixed by Twitter itself (we believed it was making an exception in Peep's regard).
Last week reports of a security leak surfaced concerning Twitter passwords being leaked and a fix, at least at that time, was offered by HTC on-demand in the form of a secure Peep application.
The Taiwanese manufacturer released an update for the HTC Touch Pro2, HTC HD2, HTC Touch Diamond2 and HTC HD mini which is apparently a security update for Peep. It might even be the secure version we heard about before being available on-demand. To apply the update, hook up your device to your PC and let it sync, download the update, transfer the EXE file to your device and run it. Being a software patch, you will need to reapply after a Hard Reset.