Hello,
We had exactly the same problem. 99% of the docs converted except the large ones. The problem is probably in the IIS configuration. This worked for IIS 7, content server build 203.
You may also run the report (SE38) RSCMSTH2 for the new repository with the size of the "large" file = 50000, you should get 404 or timeout error for the large file test.
Log in to your content server.
1) Run the IIS administration console (IIS Manger: Start - Administrative Tools - IIS Manager)
2) Select the server and click on the "Configuration Editor"
3) Find system.web - httpRuntime in the section rollout
4) Check the maxRequestLength value, it should be larger than your largest file, the size is in kB so 51200 for 50MB
5) change the value and press Apply on the right
5) Find system.webServer - security - requestFiltering in the section rollout - select requestLimits and check the maxAllowedContentLength value, the size is in bytes so 52428800 should be the value for 50MB.
6) change the value and press Apply on the right
Changes may take some time to take place and these actions can cause the content server (IIS) to be unavailable, but it recovers automatically.
Run RSCMSTH2 again, everything should be ok now.
If not, another problem may be MaxTransferBlockSize value in ContentServer.ini (server run on Windows) as described in the Note 328209. However if you have some of the newer builds installed (check in CSADMIN) I doubt changing the this value will help.
You can also set the CS logging on. Check following link:
http://help.sap.com/saphelp_nw70/helpdata/en/4c/c623476721e0448cb0028cf3fd5ecb/content.htm
and set corresponding parameters in the .file (parameters for the [ContentServer] section), then you should find the cs_trace.txt file where you can see additional info about your error. Note that full trace should be enabled only for a very short period of time only for diagnostic purposes. I dont know if a content server restart is neccessary for changes to take effect.
Good luck