Unable to Update via SMS through International Phone Number [SG]

I'm currently having issues with SMS-ing my updates from a Singapore number to the Twitter international number since 30th July 2009. I really don't get what's wrong since I have been using this service quite something. I have tried deleting my existing phone device in the Twitter page, and adding the phone number again (doing the verification via sms) but somehow it just ain't verified. Could it be the service provider problem (aka Starhub) or Twitter's side?