Im trying to upgrade the ios to c3750me-i5k91-mz.122-54.SE.bin. Using tftp it just timesout straightaway. I have removed the existing IOS so there is enough space in flash.
If you have a timeout issue there, then it's better to check if you have reachability with the tftp server. If you have connection that from what source IP?
It might be that you have to set the "ip tftp source-interface..." command in your config so that tftp process to know from where to send packets.
Again, check for ACL that might disturb your traffic.
If all this does not work, try to access the tftp server from another location and see if the service is running properly.
Let me know if this helps!