Hi Serjio
Was the unit new or s/hand, are you using it with Mac or Windows (or Linux)?
There's quite a few things you can check (put the Frame Size back to default first):
1. How is it connected to your network? Via a dedicated hub or via a broadband hub? The issue could be the LAN connection and not the box or your PC.
2. If s/hand, I would do a Disk Test and see if that reports OK. NOTE: Set up your email notification so you get a Status report sent to you.
3. If Mac, do you have it set for AFP or SMB?
4. If Windows, have you enabled SMB v2 (or higher) on both the Buffalo and Windows?
I think your starting point would be to see if you can copy data at speed to another network device, ie a share on a PC, etc and see what speeds you get. NOTE: use the same cable as you are using for the Buffalo to prove the port and cable too. If you get decent copy speeds PC to PC (1GB LAN should get around 60-80MBs) then revisit the Buffalo, else look at where the LAN issue is.
Other things to note:
1. LAN speeds are depending on the 'slowest' device on the LAN, ie if you have a 100MB switch between two 1GB devices, then the max speed is 100MB!
2. The device you are copying from or to may be busy doing other tasks
3. Speeds are very fickle as there are also file overheads, ie copying dozens of small files that take the same space as one large file will take a lot longer to copy, ie big(ger) files tend to copy faster.
4. Make sure it is not the source that it the issue, check the PC's drive too.
Hope some of this help.
Cheers