I saw a topic here, so i wrote this:
Issue #1 "I get an error <wad name>.wad is missing and game crashes to desktop"
Simply search in the RS file section for the map you were downloading and donwload it
Issue #2 "I get an error "Could not open <model name>T.mdl and game crashes to desktop.
Same as #1, download the map off the RS file section to get them
Issue #3 "I'm downloading tfc.wad/tfc2.wad/opfor.wad and it is taking ages!"
If you have an old hl install or an extracted gcf of tfc or opposing force, quite svencoop, copy them to your svencoop folder and reconnect.
Issue #4 "I get a strange error about an incorrect model version ("Mod_LoadBrushModel: MDL.mdl has wrong version number (0 should be 30)"
Delete the model file and let it re-download it off the server.
Issue #5 "I get an error stating that my <map name>.bsp is different to the server's"
Delete the map in question and re-download off the server.
Issue #6 "I get an error saying my client.dll differs from the server."
Go get the latest svencoop update off www.svencoop.com
Issue #6 "I got slowhacked somehow and now svencoop runs really slow."
Uninstall svencoop and delete the svencoop folder. then reinstall sven and try reconnecting. if it STILL runs slow, check your rate setting (type rate in console and check it is above 100, and change the setting back to your adsl/56k speed. if all else fails, uninstall and reinstall steam.
Any other problems, just ask here.
edited, thanks CsBarcodE