Contribute encountered a network or file system error. .... contact the administrator if the erro

'Contribute encountered a network or file system error. .... contact the 
administrator if the error continues to occur'

Please can someone tell me what to do? 
I have reinstalled Contribute but I still get this error message every time 
I try to edit a page. 

Bizarrely, it worked ok for a couple of days, now every time I make a connection
I get this error message. I have asked my ISP & they cannot see any problem
with their server.

Thanks

Kate