The author claimed in april, that LINQ2SQL is lighter, simpler and quicker than EF, and if You don't want to port the dataaccess to a database other than MS SQL server, this is a reasonable choice.
From that time nothig changed, the EF v.4. is the same as was in that time. (The new version is in CTP only).
Because in my application LINQ2SQL works perfectly, in your application the problem caused not by LINQ2SQL per se; maybe some settings are missed.
Switching to EF (wich isn't as easy as seemed) may not remedies Your problem.
Please let me know if found any solution