Sudden drop in Google position

I run a moderately busy forum (1000-1500 posts a day) on a third party site for the virtual world Second Life. I purchased vbSEO at the beginning of February and have been very pleased with it so far. I saw dramatic results very quickly, but something happened a few days ago that has me confused. Upon using vbSEO along with the sitemap plugin, within a week I saw my site's position in Google for the keyword search "second life forums" jump from page 9 of the results to page 2, and ever since then, it has been gradually creeping up page 2, getting as high as the third position. All of the sudden, on Wednesday, it dropped to the middle of the third page. I haven't changed anything, so I am confused at why that would happen suddenly, and wondered if anyone had any insight to why it could potentially happen.

Thanks,
Cristiano

SLUniverse.com - Second Life Community

SERPs can be quite unpredictable. Your position will typically vary from time to time. I would not be too alarmed since you only lost a few positions and are on the same page.

Your 7 page jump was fantastic.

Remember - you will always have competitors improving their SEO, as well as new competitors emerging. It is very possible that you lost a few positions versus a competitor who is actively working on their SEO for your target keywords.

Check all the positions above you to see if anyone new has emerged.

Evaluate your links. Perhaps a few new linkbacks to your page will help push you up again, eventually even breaking into page 1.

Good luck. Keep us posted with your progress.