A small number of HTC One X owners are experiencing a bug causing incoming messages to arrive without any notification pop-up. The bug, which occurs intermittently, has been acknowledged by HTC who acknowledges a bug fix is on the way. Any One X owners experiencing the issue will not see a notification warning in their status bar nor a badge on the Messaging app shortcut indicating a new message has arrived. For the moment, those experiencing the bug have to open the app itself to see if any new messages have arrived.
The problem doesn’t seem to be limited to the international version of the One X, as some AT&T units are also said to be experiencing the messaging issue as well. HTC hasn’t stated a timeline for a fix, but has promised to deliver one “as soon as possible.”