I've seen some similar problems and all. I've tried the data.myp replacement and I have done the "Read-Only" and tried to redo the Performance Counter, which I'm guessing is the problem. I tried to rebuild the Performance Counters manually.
(With these steps:)
1. Go to start, and type in the search box "cmd". Right click cmd, and run as administrator.
2. Type in the command console, "cd c:\windows\system32", and hit enter.
3. Then type "lodctr /r", and hit enter.
3. It will take a few seconds to perform the command.
Nothing has worked. The game does launch though, with the RoR launcher, but all I see is a blank Character Select Screen. The launcher gives the errors:
Data.myp:
System.InvalidOperationException: Cannot load Counter Name data because an invalid index '' was read from the registry.
at System.Diagnostics.PerformanceCounterLib.GetStringTable(Boolean isHelp)
at System.Diagnostics.PerformanceCounterLib.get_NameTable()
at System.Diagnostics.PerformanceCounterLib.get_CategoryTable()
at System.Diagnostics.PerformanceCounterLib.CounterExists(String category, String counter, Boolean& categoryExists)
at System.Diagnostics.PerformanceCounterLib.CounterExists(String machine, String category, String counter)
at System.Diagnostics.PerformanceCounter.InitializeImpl()
at System.Diagnostics.PerformanceCounter..ctor(String categoryName, String counterName, String instanceName, Boolean readOnly)
at System.Diagnostics.PerformanceCounter..ctor(String categoryName, String counterName, String instanceName)
at MYPHandler.MYPHandler..ctor(String filename, del_FileTableEventHandler eventHandler_FileTable, del_FileEventHandler eventHandler_Extraction, HashDictionary hashDic)
at RoRLauncher.Client.UpdateWarData()
And because of the constant "PerformanceCounter", I'm thinking that that is probably it. This topic's /viewtopic.php?f=4&t=441 Performance Counter fix/link wasn't loading, but I don't know.
I figure that more information might help, I've seen a few similar problems around here. And I'm probably looking the fix right in the face, but have no clue, please excuse me for that!

(Please hold back my stupidity here)