sys.dm_io_virtual_file_stats- Negative Numbers in the sample_ms Column

I have a 64-bit Windows Server 2008 R2 running 64-bit SQL server 2008 R2 version 10.50.4260. I'm seeing negative numbers in the sample_ms column when I query sys.dm_io_virtual_file_stats().  According to MSDN (http://msdn.microsoft.com/en-us/library/ms190326(v=sql.105).aspx) this column is an int representing the number of milliseconds since the computer was started.

It doesn't seem reasonable that negative numbers would ever be returned for this column.  (For that matter, it doesn't seem reasonable that you would store the number of milliseconds since the last restart in an int column- seems like the column would overflow after just a few weeks' worth of uptime.) Is anyone aware of issues with sys.dm_io_virtual_file_stats()? 

Thanks,

Vince