BlackBerry Messenger is controlled by RIM alone. There are many threads in this forum and others which address this same symptom. Usually, it occurs between the US and UK. Apparently there are fine tuning issues that have to be addressed if an OS update has been applied. You will need to contact your carrier first to verify that the provisioning is intact and up to date, then you will be referred to RIM for the resolution. Please have a known contact ready via email or landline to confirm test results when the RIM csr is working with you and sending test PINGS. Good Luck.