I replaced a faulty network card for a customer, and about 2 weeks later, I’m called back to investigate a strange network problem (with the same PC).

The PC could copy 600MB of data to another PC both quickly, and without a problem.

But try to run microsoft backup (and quickbooks backup) to backup a smaller amount of data to a network drive on another PC, and it would be very slow, and eventually give a memory cannot be written error (which usually indicates a severe hardware issue).

I do a RAM test, but its fine.

I do the backups to 2 different networked PCs (with the same results).

I look at the settings for microsoft backup, and try changing some settings (disable volume shadow copy), but the problem is still there.

Now why would some network traffic work, and not other network traffic?

Then I start thinking maybe the network card has an intermittent fault… seems highly unlikely, but possible.

Then I have an idea: maybe it needs an updated network card driver (I found a similar issue a few days prior).

I connect to MicroSloft.com, and do a windows update (I choose custom, not express), and I see that there are 4 updated hardware drivers available (one of which is the ethernet card). Once updated, All the backup problems are gone.

Its frustrating how outdated driver software can cause such problems (and other times it causes no problems at all)