Large share file copy will not start

I've just replaced a wireless router and my daily file copy from an XP share to wireless (fast - n enabled)  Windows 7 laptop now comes up with 'system cannot find the file' for the large (750kB) .pst file. Smaller .pst files will copy ok. Occasionally the file will copy using Explorer - I usually use Beyond Compare, which seems to initiate the copy successfully then decide that the source file no longer exists

 

Disabling Antivirus on the receiving laptop allows the file copy to run successfully. Both pcs are running NIS 2012. Disabling AV the other source end has no effect.

 

The previous router was a Belkin N1 Vision router, the new router is a Draytek Vigor 2830. An interim Netgear DG834T worked ok - but it had much slower throughput.

 

I can only surmise that the throughput on the Draytek causes NIS Antivirus to choke. I don't want to have to disable AV for the daily copy...

 

I tested using a gigabit hardwired link - and got the same results (copy only works with laptop AV disabled). Alas the laptop ethernet connetion speed is not configurable, but setting the source XP connection to 100Mb or 10Mb made no difference. Laptop is a Lenovo X61.

 

Regards, Keith

 

btw - just realised that the occurrence of the problem might have coincided with the latest update. Alas the Belkin died so cannot prove/disprove that this is relevent.