we faced the dotted circle problem in the 7942 phones.
I tried some of the troubleshooting methods , but no luck
1) Restart the tftp server
2) tried with the tftpd server ( with option 150 & DHCP )
tested more then 15 times, Phone detect tftp , when it trying to download the termdefault.loads , it went to dotted circle mode.
we tried with the firmware versions 8.5(4) ,8.5(3) ,8.4(3)
Any other way to resolve this ?