When running SIPDroid on my XPeria X10 (although I’ve heard of other Android phones doing the same), it appears to make one call, then after hanging up, it, well, doesn’t hang up. In short, SIPDroid seems to lock the call in place, where it continues even though it’s ended.

Not only that, but the rest of the audio on the phone stops too, until a reboot of the phone.

Here’s how I fixed it:

• Make a call.
• Note the codec it uses (shown under the call box). It will be something like “PCMA (64kbit)” or “PCMU (64kbit)” or something else technical looking^[1].
• Assuming the call fails (which is, after all, why you’re here!) go into the settings, choose “Audio Codecs”, and disable the codec you just noted. In my case, I set “PCMU (64kbit)” to “Never”
• This is the annoying bit. You’ll probably have to reboot the phone if SIPDroid won’t let you make another call.
• Once you’re back in, make another call, and note the codec. If you’re lucky, you’ll have a successful call, and no lockup. Success!
• …on the other hand, if you’re like me, you’ll have to repeat this process until it works. For me, I hit GSM before it worked.

Of course, there are other known issues at the moment, including one-way audio, issues with registering with the VOIP server, and so on. I didn’t have these issues, so if you are, you’ll have to look elsewhere I’m afraid!

^[1] …where “technical looking” means stuff like G722 HD Voice (64kbit), silk24, silk16, silk8, speex, GSM, BV16, or other supported audio codecs.

(Writing this here because I haven’t seen anything similar after much googling. Hopefully it’ll help someone!)