[c-nsp] Weird VOIP issue

[Lucas Iglesias]

Hi all,

We are having in a very weird issue. In a new 1760-V router with a
VIC2-4FXS, every time a call is tried to take place to the first port the
router shows the following error msg:

ASSERTION FAILED: file "../src-m860-les/ipm_dsprm.c", line 6018

Even though the 'show voice port summary' shows the port status in
'ringing', the phone does not ring at all and the call is lost.
The IOS Version is Software (C1700-SV8Y7-M), Version 12.3(4)T3 (file
c1700-sv8y7-mz.123-4.T3.bin)

Any ideas? 
Any stable IOS version to recommend?