Intermittent IP

[Broadshoulders]

If someone experienced this problem please provide me with some clarity on what the resolution was. I have a Business ADSL 512 connection with Telkom. As you all know currently only dynamic Public IP addresses are assigned to the WAN side of the ADSL router. For some unexplained reason I sometimes can ping my Public IP address and sometimes not (after I established what the current public IP is). The ping requests are initiated from an International destination or from a local destination other than my office. This causes huge frustrations because I have resources on my local site that need to be accessed from remote sites and if that Public IP is not available my resources can not be accessed. Help!!!! Needless to say Telkom is passing me from one department to another. The strange thing is even if the public IP is not reachable I can browse the Internet.