To find out if it is due to networking only then you should check for following :-
1. Network computers are easily accessible to each other . Files can be transfered from one computer to another easily.
If it is not so then you have to do networking again.
2. Check the connectivity by using ping command.
In case of wireless networking the ttl field of ping command should not be higher then 10ms. The command is ping 192.168.0.1 -t where 192.168.0.1 is the ip of machine which you are pinging.
3. Check if this problem is in Tally only and not in other softwares which are used over network.
If the problem is in all applications then you may need to upgrade your hardware or do the networking again. Try increasing RAM. It would help.
4. Check if memory utilization for each computer is proper.
Delete the unwanted programs from system tray or startup lists.
5. Are you using Hubs?
Switch is better option. Change it immediately.
Now comes the Tally part.
1. Check if ip's of each machine are defined.
Each machine should has separate IP in same range.
2. Your company is having more then one year data?
Split the company data and work in only current year data.
3. Tally.ini setting are correct?
IP of Tally server and proper port no. should be there for each node.
e.g. Tallylicenceserver = 192.168.0.1:9000 (server ip: port no.)
4. More then one company are opened while working?
While opening Tally default company automatically opens. We forget to shut it down before working and open our current company. Put Load Default= No in Tally ini file.
5. Is the best machine in organization is Tally server?
If no then make the fastest machine your Tally server. It would help a lot. If not working then keep the company shut.
7. What is the level of entires? How many entries you daily feed?
This thing decides a lot if number of entries are too much. In that case either switching to Tally 8.1 can help or you have to use thin client environment to work faster.
These steps would help to solve your networking problem