Hope this helps, and maybe someone else can explain the stack trace better.
Problem appears to have been caused by the TorToiseSVN vers. 1.6.16, Subversion 1.6.17, data upgrade to 220.127.116.11 Jdeveloper format. I created a new local SVN repository and did another SVN checkout. This time after the conversion to 18.104.22.168 data format, I was able to navigate in Jdev without the java.lang.OutOfMemoryError: Java heap space errors.
Deleted my local copy of <the Java> project and re-SVN checked out the whole thing again as <the other guy> did above. This did NOT solve my issue. .... Removed TortoiseSVN 1.6.99. Downloaded and installed TortoiseSVN 1.1.16. Rebooted. Removed my local SVN directory of project files. Created a new local directory of project files. SVN Checkout into the new directory. Error seems to be resolved. It's not clear exactly what in SVN (or which versions, as <the other guy> is still running 1.6.99) is causing this, but it seems to be related to some version/corruption issue between jDev and SVN, and it renders jDev unusable.