Does it say which file is conflicted? Usually if there is a conflict in the modeler you can right click the conflict in the changes doc and choose to resolve with yours or theirs. If a file outside of the modeler is conflicted (for example a sass file), you would have to use tortoise svn to resolve the conflict.
The documentation has a link to download tortoise svn. Make sure to download version 1.7 and not the latest version (this important).
The section about tortoise svn and subclipse has the link:
Once you download svn you can open up file explorer and right click the folder that contains your project, go to TortoiseSVN > Check for modifications.
Once you click that a dialog box will appear. The file that is conflicted will have a status of conflicted. Right click that file and choose resolve using yours or resolve using theirs.
Resolve using yours will use your copy and resolve using theirs will use the version control copy.
Once all conflicts are resolved you should be able to commit.
Hope this helps!