I don't know what you've tried, so apologies if you've already tried these.

Cut back the number of files you have waiting to d/load to 1 or 2. Sometimes if you have too many files queued, it'll cause unwanted side effects.

Defrag your hdd if you haven't already. You could also scan your hdd for errors. Go to Start > My Computer > right click on the drive your using(normally C:) > Properties > Tools > Error Checking > check Now > "Scan for and attempt recovery of bad sectors" (check box).

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