Onofras Ioan,
in most cases, clearing the cache helps. To clear the cache, do the following:
Method 1.
1. In the list of infobases, click your infobase, then click Settings.
2. In the Configuration template and update directories field, find a path that looks like this: C:\Documents and Settings\username\Application Data\1C\1Cv8\tmplts\1c.
3. The path to the cache folder will look like this: C:\Documents and Settings\username\Application Data\1C\1Cv8\. Open this folder.
4. You will see a lot of folders with names like this: 0a3fb881-abde-4208-839d-0f80874cb3cb. Delete them all.
Method 2.
Remove the infobase from the list, then add it back. This does not actually delete the old cache files, it simply assigns a new cache folder to the infobase.
Method 3 (thin client only).
Run the platform with /ClearCache parameter.
If clearing the cache does not help, verify and repair the infobase. In Designer, on the Administration menu, click Verify and repair.
Please let me know if this helped.