Quite a few of us have been affected by a problem with the Diablo 3 launcher. It seems to start OK (clicking on INFO gives the relevant download info). However, the progress bar doesn’t move and the PLAY button remains gray (inactive).
Here’s a few solutions to try:
1) Exit launcher, go to the DVD and start the Diablo III Setup.exe. It will force the launcher to start again and it worked for me on first try.
2) Click Diablo III (via the shortcut or Diablo III Setup.exe) and select “Run as Administrator…”
3) Turn off all anti-virus programs as they slow down the update (a thousand new files to check). Be patient and wait for a few minutes (if you have done solutions 1 or 2).
4) Kill agent.exe and re-open the launcher. This has worked for people getting the ‘failed to read required file’ error. I got the error but retrying Diablo III didn’t work, I had to re-try the Setup file on the DVD.
If you decide to contribute your solution to the launcher problem, post it at this technical forum!
Don’t get too frustrated about this error because even people who managed to get the launcher to update everything are stuck at the login servers which seem to be under a lot of pressure. Everyone is getting either server busy errors (37) or Battle.net service outage error (75).