Http server failing => CheckFailure

C2 r50; Windows XP SP3; FireFox 5.0; ATI Radeon HD 4800

I click to start the preview.

During start of layout

=>

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Construct 2 Check failure

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Check failure! This is probably a bug:

Cannot find file on disk to return over HTTP

Condition: FileExists(disk_path)

File: HttpFileServer.cpp

Line: 228

Function: void __thiscall HttpFileServer::ServerRespond(struct _HTTP_REQUEST_V2 *)

Build: release 50 (32-bit) checked

Component: HTML5 exporter

(Last Win32 error: 2)

You are using a 'checked' release of Construct 2, intended for testing, which causes certain errors to be reported this way. Hit Ctrl+C to copy this messagebox - it's useful information for the developers, so please include it with any bug reports! Click 'Abort' to quit (unsaved data will be lost!),'Retry' to turn off messages for this session and continue, or 'Ignore' to continue normally.

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And I have a bug in runtime (Missing sound files which haven't been saved in the project folder).

Cause & effect ?

I copied the files from a previous backup, relaunch C2, the preview works.

Also it appears to do with the fact that when creating a new folder (out of C2), saving the current opened Project in C2 (with sound files) in the new project folder, the sound files don't get copied after a while.

I have to manually copy the content from the folder "files" from a previous backup to the new one, unless I get error "missing files" on opening the project.

That happened right around the time of this check failure (I saved a project, C2 crashed, reopened it, save to a new folder, file sounds wouldn't copy).