When using Sharepoint Designer you could notice that some options are missing an example is when i was customising a DataView webpart.I wanted to add some Filtering options so i clicked on the property menu and then to
Common Dataview Tasks > Filtering > selected my FIledName and next was the Comparision but selecting that i noticed that the "is Greater than or equal to" and "Greater than" options were missing. If i remembered more than 3-4 options were missing if not more.
And this was the options i wanted to use for my filtering 
.
I did post to some newsgroups and tried to look for a solution but no luck. So the first thing that came to my mind was SECURITY.
My last option was to dig into it.So what i did was on one of my dev machine i installed another sharepoint designer and tried using that to hook into another instance of WSSv3 based on the same scenario.
So i added one site to a trusted zone with the FQDN and the other one without. When plugging in into SharePoint Designer i didn't use the FQDN which means i just went http://intranet:portNO instead of http://domainname:portno and logged in normally.On that machine i could see the options 
i wanted but if i use the FQDN the options disspeared.
So it seems sharepoint designer wasn't having enough access to get to the remaing options BUT THAT WAS MY WAY AROUND IT. Which seems it must me a permission issue.But wierd though since 'm an ADMIN on these sites.
Hope that saves your time and if you have more info on this please let me know because it could be fustrating