All empty cells in the spreadsheet formatted as time

For some inexplicable reason all empty cells in my multi tab dashboard spreadsheet are formatted as time. When mouse over on some series in graphs value shows as time too. Moreover, when exploding pivot into detail worksheet every single value in that detail sheet is formatted as time too. Has anyone experienced such annoyance? Had I inadvertently changed default formatting for the file to be the "time"?

Greatly appreciate any feedback.

Thanks,
Igor

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An example of pivot detail, have to change all columns to corresponding data format to be able to use it...

The cause - style "Normal" corrupted through imports. Found the utility that resolved the issue here: http://sergeig888.wordpress.com/2011...now-available/