I found this article and hoping this can lead you the way to a resoltuion (link provided at bottom)
* Step one – establish the baseline – like in the prior blog post, the best thing to do is to establish that it is truly Sharepoint doing the ‘sucking’ of the RAM. If it is, reboot the server and record the amount of RAM Sharepoint is now using ‘after’ the reboot.
* Step two – build a baseline value – watch the Sharepoint instance for a few days, how long before it starts ‘ticking up’? You can get a ‘feel’ for where that ‘throttle value should be by watching it for a few days.
* Step three – do you have enough RAM in the machine? For SBS 2000 I had 2 gig, for 2003 I have 4 gig. Most are comfortable at about a 2 gig level on SBS 2003 [I tend to overbuy]
* Step four – is your page file large enough? If you have the RAM in place at the time of building the machine, your paging file is about 1.5 times your physical ram. If you add RAM later, you’ll need to adjust this manually.
* Step five – ask yourself, are your applications truly slowing down by this? Do you see true performance impact?
* Step six – Is it just that you have a lot of things going on in your box? Les has a box that throws off these allocated memory alerts but he’s got like three Virtual machines running under it, look at the services running on that server and none of them look bad at all. What you are truly looking for is one of the services not ‘settling down’ as I would call it. Again, if it’s just SBSmonitoring, I’d adjust that with no hesitation. For anything else, I’d monitor and call.