Trying to understand something on Activity Log

I have read some of the posts on here and would like to ask a 2 questions about the Activity log and what things mean.

I notice that the activity log notes when programs access the internet, example internet explorer.

I also know that it will indicate when unused ports are blocked by outside attempts to enter, which appear to happen every hour or so, but just 1-3 entries.  But I have an entry which I’m not sure off.

I notice that every 2-3 minutes I get an entry that reads Port blocking allowed 192.168.2.1 1.

I know that 192.168.2.1 is the router, but not sure why it keeps showing on my activity log every 2-5 minutes.

1. Is it because the activity log itself continues to “monitor”” any connections? 

2. Is it common to have a few attempts every hour to 90 minutes of some IP address trying to connect to an unused port?    These get blocked, so I’m not worried. Just curious 

I have an HP Desktop running Windows Vista OS with the Vista Service pack 1 and Norton Antivirus 2008