What analytics service do you use?
schammy: You won't find any analytics service that gives you numbers anywhere close to server logs. This is because log analyzers include all search engine / robot / spambot activity. All hosted analytics (e.g. ones that use javascript and don't have access to your logs) will only report human activity, and seeing 50% less traffic shouldn't come as a shock for this reason. It doesn't mean they're inaccurate, but if robot activity is important to you, you won't find a service you're happy with.