i was updating to os 4.5. then i got a message on my phone saying app error 523. i didnt back up my stuff on my phone. but that doesnt matter anymore because i dont even have a phone that works. i just got this one after my last bb got stolen. please help. please.

No problem, just read the FAQs, and later the sticky at the op of the the 83xx section
General 8300 Series Discussion - Curve - BlackBerryForums.com : Your Number One BlackBerry Community

You will find the last OS and the instruction of how to install...

app error 523 is caused by a conflicting 3rd party app or theme. Remove the battery and reinsert. While the hourglass is spinning run Loader.exe (found in c:\program files\common files\research in motion\apploader) and remove the offending 3rd party app.