Like me. Now I installed the HTMLViewer package (I guess that's what you mean) via Online Package Manager into Lazarus trunk / fpc 3.0.4 -- and see the same error message. I have another installation of Laz trunk with fpc 3.1.1, and here the package seems to work correctly, I checked a sample demo - no problem.
So, I guess, you should update fpc to the trunk (or maybe fixes) version. You can use fpcupdeluxe for an easy installation.
[EDIT]
Now I tried Laz1.8/fpc 3.0.4, uninstalled ImagesForLazarus and installed HTMLViewer -- no problem. Installed ImagesForLazarus again -- problem. I think you did something wrong when you uninstalled ImagesForLazarus. Did you rebuild the IDE?
Looking at ImagesForLazarus I don't see much to be missed. Most of the units add deprecated aliases to graphics image types (TJPGImage instead of TJPEGImage, TPngImage instead of TPortableNetworkGraphic, etc). The only unit in which a little bit is "happening" is the one which registers the tga support. I don't see big problems is this package is not installed.