Help Help Help! Im tearing my hair out with this problem...

When users have woken their PC from sleep, randomly they cannot access a DFS mapped drive letter (well they can browse the first level but not go any further) it simply says H:\BLAH\Blah is unavailable...
Googling comes up with nothing, and no MS hotfixes works...

If i reset the CSC Offline Cache that seems to correct it for a week or so but then it goes again! Its a real pain in the a**e!!! Anybody seen this before?

Mart