According to HTC's official Twitter account, Twitter and the manufacturer have ironed out the bugs that were created when Twitter changed its authorization system a few days ago and broke both Peep and Friend Stream logins:
I have tested it on my EVO and can confirm that it is working properly. I'm not sure how such a major screwup could have fallen through the cracks at HTC, but let's hope it won't happen again. Read More
Well, this is somewhat entertaining (probably because I don't use Peep - those of you who do probably find it a lot less funny). Twitter flipped the switch on an application login change on Monday, and as a result users can't login to Twitter through HTC Peep. It's a bit difficult to understand without going into more detail, so without further ado, more detail.
Previously, applications could use one of two ways to login to Twitter: Basic Authentication and OAuth. The Twitter devs say it quite nicely, so I'll just do less work and quote them:
In order for Twitter applications to access your account, developers have been able to choose one of two authentication methods: Basic Authentication or OAuth.