Not sure exactly how we ran into this, but for some reason one of our 2008 Reporting Services servers would only allow us to upload RDLs that were less than ~105k. Couldn’t find much online so we ended up calling Microsoft to figure out what the deal was. Turns out here is a registry key that needs to be in place to remedy this situation.
Add a REG_DWORD with the name MaxRequestBytes and a hex value of 500000. You will be able to upload larger RDLs now.