We recommend using Netfabb to check and scale your designs before uploading them to our site. It is free to download at http://www.netfabb.com/
We use this for all our file checking and STL repairs so you can be sure that if Netfabb says the mesh is good it will upload to our site.
Netfabb doesn't open DAE files but there are 2 ways to get a Sketchup design into Netfabb
- Export an OBJ file and open that directly
- Download the plugin for creating STL files. Follow the instructions on this page to install an STL plugin for SketchUP -http://www.guitar-list.com/download-software/convert-sketchup-skp-files-dxf-or-stl
Open the OBJ or STL in Netfabb to fix any mesh errors and check the size of your objects. You can read our guide for the basic steps here - http://support.ponoko.com/entries/20181756-Self-check-your-3D-designs-with-Netfabb
Save as a binary STL file to keep the size down and then you should be able to upload it fine.