This might sound silly but it has happened to me recently and like you have had very little messages or phone usage. Go to the message that states "sending" and delete that message. go back to the original source or picture and resend it. try that out. the key part is to delete the message causing the error and just start fresh. let me know if it helps.
I would recommend this doc: http://support.t-mobile.com/docs/DOC-1976
Checking the Access Point Name (APN) is useful when you cannot access the internet, have no data connection, or picture messages (MMS) are not sending.
T-Mobile myTouch 3G / 3G Slide / 4G devices that are updated to Android 2.2.1 have a problem with picture messaging (MMS) due to a TelKila APN. You must modify the APN settings as described below.
To verify that the APN and internet data connection settings, follow these steps:
- Verify the Airplane mode check box is cleared, so that the wireless radio is on.
- Verify that the Mobile network check box is selected so that you can connect to data networks.
- Touch Mobile networks.
- Verify the Data roaming check box is selected. This will incur charges if you roam internationally, but it is required to receive data when roaming domestically.
- Delete any connection listed for TelKila or T-Mobile MMS. To delete them:
Important: If you perform a master reset or reset the APN to default, any problems you had with the APN will return and cause connection problems again. You must perform this procedure again.
- Note: If you cannot delete TelKila, then edit the MMSC field to: http://mms.msg.eng.t-mobile.com/mms/wapenc
- Touch the T-Mobile Data (or T-Mobile US) connection to view its settings.
- Verify the following:
- Name: T-Mobile Data (or T-Mobile US)
- APN: epc.tmobile.com
- Proxy: <Not set>
- Port: <Not set>
- Username: None
- Note: For the Username, enter "None" with the keypad. Do not leave it not set.
- Password: <Not set>
- Server: <Not set>
- MMSC: http://mms.msg.eng.t-mobile.com/mms/wapenc
- MMS proxy: <Not set>
- MMS port: <Not set>
- MMS protocol: WAP 2.0
- MCC: 310
- MNC: 260
- Authentication type: <Not set>
- APN type: default,supl,admin,dun,mms
- Press the Menu key.
- Touch Save.
- Verify that you only have one T-Mobile Data (or T-Mobile US) connection listed.
Note: Resetting the APN and master reset both can cause the TelKila APN to return, so it is NOT recommended. However, if you need to reset: From the Access Point Names screen, press the Menu key, and touch Reset to default.