Changing Filename Case with TortoiseSVN on Windows
Use Rename option in Tortoise SVN from popup menu. See details here ("Moving files and folders" chapter).
When you changed the case of several file names, in other words you changed file names - they have become out of version control - that's why SVN client noticed that files that was under version control had disappeared (apparently, that happened because SVN client wasn't informed properly).
If you happened to be in this situation when IDE or you changed the case accidently - there is special menu option Repair move which appears when you select both files that are shown as "missing" and "non-versioned". Check this.
I found that Tortoise SVN has a setting for auto fixing file name case changes. It is set to true by default, so if you only change the case of letters in the name then it will undo your changes for you... silently and ruthlessly I might add, very annoying default setting in my opinion.
Anyway luckily if you navigate to TortoiseSVN Settings->Advanced->FixCaseRenames you can change it to false and it will no longer auto correct case changes.Setting Location