Infrastructure Software

I'm trying to transfer files using SCP/SFTP between Solaris 10 systems and between Solaris 10 and Red Hat Linux 5.4 systems. Between Solaris machines, there doesn't seem to be a problem. However, when trying to transfer from Solaris to/from the RHEL system, transfers always stall at approximately 22M. I've tried reducing the mtu on the RHEL system (+ifconfig eth0 mtu xxxx+) and this does increase the limit before it stalls, but still anything above 45M cannot be transferred. There are no quotas set on any system and there is plenty of disk space. Searching on the web did not yield any useful ideas.
I can use Putty on a Windows system to act as an intermediary, getting from the Solaris system and putting to the Linux system, and transfer a 115M file okay. This is obviously a clunky work-around and doesn't allow for scripting of transferring files. This would seem to be a problem with SSH on the Linux system I'm guessing, although I haven't been able to rule out something on the Solaris system - what parameters in SSH configuration control this? Why did changing the mtu change, but not eliminate, the problem?