I made a blog post last year that addressed these errors and some steps to try to resolve them. If you have found that even after following all the steps I provided you still seem to have the errors, you are not alone. This is actually a recognized memory leak with the owstimer service in the MOSS code.
In the past I have installed WSS and MOSS Service Pack 1 to resolve the owstimer memory leak, and try this first. Many times these errors will resolve with the service pack. However, If you notice that these errors reappear then you will have install this hotfix from Microsoft. I have tested the hotfix and can report great success with it. However, with all hotfixes try the Service Pack first.
