Error for a grid in grid

I get this error with firebug

for a grid with subgrids :

oTidyBrowser is not defined

[Break on this error] if (r._childIndexes)

oTidyBrowser is not defined
Such name never used in code of grid, please check your custom code.

>>[Break on this error] if (r._childIndexes)
It hard to say, but most probably you have used incorrect ID or not existin Index in some command.

If problem still occurs for you - please provide any kind of sample where it can be reconstructed.